Literatura académica sobre el tema "Prospective longitudinal design"

A growing body of research conducted in general life settings has found positive associations between happiness and prosocial behavior. Unfortunately, equivalent studies in the workplace are lacking. Organizational citizenship behaviors (OCBs), the prosocial behaviors at work, have not been properly studied in relation to happiness, despite the positive consequences of both constructs for workers and companies. In response, our research aims to better understand this relationship from several angles. First, using a three-wave longitudinal design, we explored how OCBs and happiness are related to each other over time. Second, happiness was measured from a broad perspective, and three conceptualizations were adopted: the hedonic (e.g., positive affect and life satisfaction), the eudaimonic (e.g., relatedness and autonomy), and the flourishing (e.g., meaning and engagement) approaches. Thus, not only the prospective link between OCBs and happiness was tested, but it was also explored using the three models of happiness previously mentioned. Third, we conducted this longitudinal design in a less typical sample than previous research (i.e., Chile). We found results that supported our main hypotheses: (1) OCBs are prospective positive predictors of hedonic happiness, eudaimonic happiness, and flourishing; (2) the three models of happiness also prospectively predict OCBs. Our findings suggest that OCBs foster a broad range of happiness facets, which in turn fosters back the emergence of more OCBs, leading to a virtuous circle of prosociality and well-being in the workplace. This positive spiral benefits not only workers’ quality of life, but also organizations’ profitability and sustainability. Theoretical and applied implications for the field of Positive Organizational Psychology are discussed.

Background: Cortical thickness (CT) and gyrification are complementary indices that assess different aspects of gray matter structural integrity. Both neurodevelopment insults and acute tissue response to antipsychotic medication could underlie the known heterogeneity of treatment response and are well-suited for interrogation into the relationship between gray matter morphometry and clinical outcomes in schizophrenia (SZ). Methods: Using a prospective design, we enrolled 34 unmedicated patients with SZ and 23 healthy controls. Patients were scanned at baseline and after a 6-week trial with risperidone. CT and local gyrification index (LGI) values were quantified from structural MRI scans using FreeSurfer 5.3. Results: We found reduced CT and LGI in patients compared to controls. Vertex-wise analyses demonstrated that hypogyrification was most prominent in the inferior frontal cortex, temporal cortex, insula, pre/postcentral gyri, temporoparietal junction, and the supramarginal gyrus. Baseline CT was predictive of subsequent response to antipsychotic treatment, and increase in CT after 6 weeks was correlated with greater symptom reductions. Conclusions: In summary, we report evidence of reduced CT and LGI in unmedicated patients compared to controls, suggesting involvement of different aspects of gray matter morphometry in the pathophysiology of SZ. Importantly, we found that lower CT at baseline and greater increase of CT following 6 weeks of treatment with risperidone were associated with better clinical response. Our results suggest that cortical thinning may normalize as a result of a good response to antipsychotic medication, possibly by alleviating potential neurotoxic processes underlying gray matter deterioration.

Abstract Background Amphetamine-type stimulants (ATS) have become a critical public health issue. Animal models have indicated a clear neurotoxic potential of ATSs. In humans, chronic use has been associated with cognitive deficits and structural brain abnormalities. However, cross-sectional retrospective designs in chronic users cannot truly determine the causal direction of the effects. Objective To prospectively determine effects of occasional ATS use on cognitive functioning and brain structure. Methods In a prospective longitudinal study design, cognitive functioning and brain structure were assessed at baseline and at 12-month follow-up in occasional ATS users (cumulative lifetime use <10 units at baseline). Results Examination of change scores between the initial examination and follow-up revealed declined verbal memory performance and putamen volume in users with high relative to low interim ATS exposure. In the entire sample, interim ATS use, memory decline, and putamen volume reductions were strongly associated. Conclusions The present findings support the hypothesis that ATS use is associated with deficient dorsal striatal morphology that might reflect alterations in dopaminergic pathways. More importantly, these findings strongly suggest that even occasional, low-dose ATS use disrupts striatal integrity and cognitive functioning.

A study is presented on the influence of criminal victimization on well-being and fear within a nationwide sample of the Dutch population. The study focused on differences between victims and non-victims, and on the causality between crime and psychological upheaval. The design of the study was prospective, it included victims of several crime-types, and a matched sample of non-victims. The reactions of victims were measured before, and within two weeks, one month and two months after the crime. Results indicated that victims of crime systematically report lower levels of well-being, and, to some extent, higher levels of fear. Next, some indications were found supporting the notion that victims of violent crimes suffer more psychological distress than victims of property crimes. And finally, the data imply that, after the incident victims were ‘unhappier’ than non-victims, but, at least partly, already were so before the crime took place.

This article explores dynamic capability formation in new ventures examining technology commercialization at the microlevel of entrepreneurs’ actions and decisions. The research reflects a longitudinal, qualitative, multi-case study design to build theory. Findings reveal two interdependent micro-level patterns that reflect dynamic entrepreneurial capabilities. First, prospecting problems or the capacity to identify problems in industrial settings that a commercially untried technology might solve. Second, openly sharing technological features with prospective customers in order to jointly design prototype products. Revealing technology helped ensure new venture survival in contrast with conventional wisdom that links firm survival to the insulation and protection of technology. Moreover, micro-level patterns shaped macro-level change in venture/customer dyads and in related customer’ industries.

ObjectiveTo evaluate multiple determinants of the longitudinal change in insulin clearance (IC) in subjects at high risk for type 2 diabetes (T2D).Research design and methodsAdults (n=492) at risk for T2D in the Prospective Metabolism and Islet Cell Evaluation cohort, a longitudinal observational cohort, had four visits over 9 years. Values from oral glucose tolerance tests collected at each assessment were used to calculate the ratios of both fasting C peptide-to-insulin (ICFASTING) and areas under the curve of C peptide-to-insulin (ICAUC). Generalized estimating equations (GEE) evaluated multiple determinants of longitudinal changes in IC.ResultsIC declined by 20% over the 9-year follow-up period (p<0.05). Primary GEE results indicated that non-European ethnicity, as well as increases in baseline measures of waist circumference, white cell count, and alanine aminotransferase, was associated with declines in ICFASTING and ICAUC over time (all p<0.05). There were no significant associations of IC with sex, age, physical activity, smoking, or family history of T2D. Both baseline and longitudinal IC were associated with incident dysglycemia.ConclusionsOur findings suggest that non-European ethnicity and components of the metabolic syndrome, including central obesity, non-alcoholic fatty liver disease, and subclinical inflammation, may be related to longitudinal declines in IC.

In this article, we share our experience of navigating qualitative longitudinal research with a ‘hard to recruit’ population. To detail design conception, methodological challenges and insights, we draw on the case of a 1-year-long study on health behaviour in Olympic hopefuls. In order to accompany 12 athletes who aimed to qualify for either an Olympic Games (n = 10) or a World Championship (n = 2), we developed and implemented a career background questionnaire; semi-structured interviews; weekly web surveys; a training observation and a compilation of competition results. Based on the longitudinal research experience, we present project management and project data of the Paths-to-Rio study to discuss the challenges we faced, including gaining access to an elite population, their retention and anonymity. We further outline insights the prospective study gave us on the value of missing data as data and on the benefits participants described in terms of learning through research involvement. We conclude with recommendations for future qualitative longitudinal research.

The objectives of the community-based Early Developmental Stages of Psychopathology (EDSP) Study are described along with a detailed account of the overall design, special design features, sample characteristics and instruments used. The EDSP employed a prospective-longitudinal design to study substance use and other mental disorders in a representative population sample of 3,021 subjects aged 14–24 years (birth cohorts 1970–1981) at ‘baseline’ – the outset of the study. Two follow-up investigations were conducted after the baseline investigation covering an overall period of 3–4 years. Special design features are the linkage with a family supplement (EDSP-FS) as well as neurobiological laboratory studies of high-risk subjects.

The objectives of the community-based Early Developmental Stages of Psychopathology (EDSP) Study are described along with a detailed account of the overall design, special design features, sample characteristics and instruments used. The EDSP employed a prospective-longitudinal design to study substance use and other mental disorders in a representative population sample of 3,021 subjects aged 14–24 years (birth cohorts 1970–1981) at ‘baseline’ – the outset of the study. Two follow-up investigations were conducted after the baseline investigation covering an overall period of 3–4 years. Special design features are the linkage with a family supplement (EDSP-FS) as well as neurobiological laboratory studies of high-risk subjects.

Les résultats de la recherche portant sur les impacts de la jalousie dans les relations de couple sont mixtes et ne nous permettent pas d’en connaître son impact sur le désengagement romantique, ou la perte de sentiments amoureux, qui est un problème fréquemment mentionné par les couples qui consultent en thérapie conjugale. Par le biais d’un devis longitudinal et dyadique, cette étude a examiné l’association entre la jalousie et le désengagement romantique, en tenant compte de la satisfaction relationnelle à titre de facteur modérateur. Concernant les effets acteurs, vu l’état actuel de la recherche portant sur l’effet de la jalousie sur différentes variables relationnelles, aucune hypothèse n’a été émise concernant la direction de l’association entre les trois composantes de la jalousie et les changements dans le désengagement romantique chez l’individu 9 mois plus tard. Cependant, nous avons émis l’hypothèse que la satisfaction relationnelle modèrerait cette association à travers le temps. Concernant les effets partenaires, nous avons émis l’hypothèse que de hauts niveaux de jalousie chez l’individu seraient associés à une augmentation du désengagement romantique chez son partenaire à travers le temps. Nous avons également considéré les différences de genre dans ces effets acteurs et partenaires. La jalousie, le désengagement romantique et la satisfaction relationnelle de 141 couples de sexes mixes ont été mesurés à deux temps de mesures sur une période de 9 mois. Des analyses acheminatoires basées sur le Modèle d’interdépendance acteur-partenaire ont ensuite été effectuées afin de vérifier les questions et hypothèses de recherche. Les résultats ont montré que la jalousie émotionnelle chez la femme était associée à une diminution de leur propre désengagement romantique à travers le temps (β = -.154, p = .029). De plus, la satisfaction relationnelle modérait l’association entre la jalousie émotionnelle et le désengagement romantique, c’est-à-dire que les femmes rapportaient une diminution de leur désengagement lorsqu’elles rapportaient être faiblement (B = -0.016, p = .004) ou moyennement satisfaites dans leur relation (B = -0.011, p = .032). L’interaction n’était pas significative pour les femmes qui étaient très satisfaites (B = -0.006, p = .257). La satisfaction relationnelle modérait aussi l’association entre la jalousie cognitive et le désengagement romantique chez la femme. La jalousie cognitive était associée à une augmentation du désengagement, mais seulement chez les femmes qui rapportaient être extrêmement satisfaites dans leur relation (4 ÉT au-dessus de la moyenne; B = 0.024, p = .048). Par ailleurs, la jalousie comportementale de la femme permettait de prédire une augmentation du désengagement chez son partenaire (β = .142, p = .039). Les résultats suggèrent que la jalousie serait un facteur à considérer pour comprendre le désengagement chez les couples de longue durée au fil du temps. De plus, cette association serait modérée par la satisfaction relationnelle, mais pour les femmes seulement. Des études supplémentaires seront nécessaires afin d’identifier d’autres facteurs relationnels et personnels pouvant contribuer au désengagement romantique chez l’homme.
Research examining jealousy among couples provides mixed findings regarding its association with relationship outcomes and does allow an understanding of its role in romantic disengagement. Also referred to the process of falling out of love, disengagement is frequently reported by couples who seek relationship therapy. Using a dyadic and prospective design, the purpose of this study was to examine the association between jealousy and romantic disengagement while considering relationship satisfaction as a potential moderating factor. Since the current literature provides mixed findings about the effect of jealousy on relationship outcomes, no a priori hypotheses were proposed about the directionality of the associations between the three components of jealousy assessed at baseline, and changes in romantic disengagement for the individual 9 months later (actor effects). However, we expected that relationship satisfaction would moderate this association. At the dyadic level, we expected that high levels of jealousy in the individual would be associated with an increase in their partner’s level of disengagement at follow-up (partner effects). Finally, we also considered gender differences in actor and partner effects. Jealousy, romantic disengagement, and relationship satisfaction were assessed twice among 141 mixed-sex couples over a nine-month period. Path analyses using the Actor-Partner Interdependence Model were conducted to verify the hypotheses and research questions. Emotional jealousy was related to a decrease in one’s romantic disengagement over time for women (β = -.154, p = .029). Moreover, relationship satisfaction moderated the association between emotional jealousy and disengagement— women who reported low (B = -0.016, p = .004) to moderate (B= -0.011, p = .032) levels of relationship satisfaction experienced a decrease in their disengagement, but not when they reported being highly satisfied (B = -0.006, p = .257). Relationship satisfaction also moderated the association between cognitive jealousy and romantic disengagement for women—jealous thoughts were associated with an increase in romantic disengagement when women reported extremely high levels of satisfaction (4 standard deviations above the mean: B = 0.024, p = .048). Additionally, women’s behavioral jealousy predicted an increase in their partner’s disengagement (β = .142, p = .039). The findings suggest that considering jealousy increases our understanding of disengagement and how it unfolds over time among long-term couples. Moreover, relationship satisfaction would moderate the association between jealousy and disengagement, but only for women. Further research is required to identify other relational or personal factors that could contribute to romantic disengagement in men.

We describe the initiation and evolution of the Berkeley Girls with ADHD Longitudinal Study, an ongoing prospective, longitudinal study of 140 girls diagnosed with ADHD when they were children during the late 1990s, as well as 88 matched comparison girls. Study rationale, design, procedures, recruitment strategy, and measures are described in detail. Primary psychosocial and neuropsychological findings during childhood, adolescence, and adulthood are summarized. Our initial findings regarding predictors of outcome are presented. Results are discussed in light of the existing literature regarding long-term outcome among children with ADHD. Overall, during childhood, adolescence, and young adulthood, in almost every psychosocial and neuropsychological domain we investigated, females with ADHD show sizable disadvantages and deficits relative to females without ADHD. Our findings affirm the public health significance of ADHD in girls, given the likelihood of persisting symptoms and (especially) impairment in crucial domains over the long-term.

The literature on post-traumatic growth has been instrumental in highlighting the human capacity to overcome adversity by illuminating different pathways that individuals may follow when confronted with adversity. However, while the theme of “strength from adversity” is attractive and central to many disciplines and certain cultural narratives, these claims lack robust empirical evidence. Specific methodological issues include the ubiquity of retrospective assessments of post-traumatic growth. Conceptually, limitations exist in the examination of which outcomes are most appropriate for studying post-traumatic growth. The authors present an overview of directions that new research should focus on in order to overcome these limitations, with a focus on prospective longitudinal designs that incorporate multiple methods of assessments and the value of integrating these disciplines for furthering our understanding of the human capacity to overcome adversity. The book is divided into four substantive sections to more thoroughly examine the conceptual and methodological limitations of this literature: (1) current challenges in examining post-traumatic growth, (2) methodological advancements (with a focus on innovative assessment strategies), (3) research in specific populations (cancer survivors, US minority communities, armed forces personnel and older adult samples), and (4) new directions for research (focusing on examining event characteristics of adverse events as well as narrative identity, wisdom, and open-mindedness as key growth outcomes).

Types of psychiatric disorders vary with respect to age of onset, temporal continuity, and impact. Life course epidemiology provides powerful tools for understanding these complexities. This discipline broadly distinguishes ‘sensitive period’ and ‘risk accumulation’ models. The former refers to optimum windows for exposure (e.g. early life for some psychoses, in contrast to proximal exposures for depression). Accumulation refers to additive or multiplicative effects of multiple exposures, exemplified by stress process and chain of risk models. The preeminent study design for these approaches is the prospective longitudinal birth cohort study, especially where multiple cohorts help to distinguish period and cohort effects. However, limitations such as balancing the need for repeated versus age-appropriate measurement, and non-random missing data, must be carefully considered. While the statistical workhorse for life course epidemiology is general linear modelling, this discipline also requires advanced tools such as random effects, path, latent class, and latent growth modelling.

The authors discuss the promise of innovative mixed-methods research designs for examining whether the type of narrative that individuals construct after committing an act of interpersonal failure leads to the development of empathy and humility over time. They define acts of interpersonal failure as the mistakes and wrongdoings individuals commit during their romantic relationships and focus on interpersonal failure, because a certain degree of conflict is expected in most relationships and can offer individuals an opportunity to reflect on the type of partner they want to be in the future. The authors discuss this question cross-culturally through the lens of quantitative and qualitative research designs, an approach that will permit the examination of whether the cultural narrative influences how people narrate stories of adversity, challenge, and failure across nations. The authors further discuss culturally sensitive coding schemes that can be applicable to future research that use a prospective longitudinal quantitative repeated-narration design to investigate whether intra-individual variation in the narrative construction of interpersonal failure over time leads to increases in humility, empathy, and greater engagement in pro-relationship behaviors. Thus, this research project examines whether narration is a mechanism for learning from interpersonal failures to develop and flourish within relationships.

This chapter focuses on conceptual notions and methodological approaches for examining whether post-traumatic growth is possible in older adults, with an emphasis on individual and dyadic approaches. A majority of the literature to this point has focused on examining changes in the individual who experienced the traumatic event, but much less is known regarding how a partner or spouse responds to the traumatic event. This chapter discusses how the use of multimethod prospective longitudinal measurement burst designs can provide insights into this growth following a traumatic event. The authors discuss as an example the case when at least one partner is planning to transition into assisted living. An increasing number of individuals reaching old age must make the decision to transition into an assisted living or similar type of home. The use of multimethod prospective longitudinal designs enables the researcher to delineate the extent to which character virtues may change on different time scales in terms of state character virtues assessed in daily life (e.g., how altruistic a person is in a given moment or day) versus trait characteristics (e.g., how altruistic a person is, on average) and elucidate hypothesized transactional mechanisms (e.g., individual differences, dyadic, and contextual factors, such as experiences of daily stressors) that may promote or inhibit changes in character virtues.

Developing new treatment options for individuals with ASD requires identifying the mechanisms that underlie core symptoms throughout the lifespan. Case-control designs are still very common but have well-recognized limitations; cutting-edge research combines large samples, prospective longitudinal designs, measures that can be back-translated to animal models, and advanced genetic techniques that identify common neuropathology. Insights from clinical studies have identified social attention as a putative early signature of autism emergence that may be modifiable with behavioural or pharmacological treatment, but evidence that reduced social attention has downstream effects on other social difficulties remains limited. Preclinical and genetic work has identified converging alterations in synaptic function, activity-dependent translation, oxidative stress, and immune dysfunction; some differences may be reversible in animal models, but successful human clinical trials remain rare. Moving forward requires greater integration of clinical and preclinical insights, and more focus on understanding variability across the spectrum.

Patients and their caregivers commonly report positive psychological change following the diagnosis and treatment of cancer, a phenomenon referred to as perceived growth. However, most studies have examined patient and caregiver growth as separate, parallel processes, without considering their dynamic interplay or the shared interpersonal context. Furthermore, previous research is limited by cross-sectional designs that use retrospective self-report measures to capture perceived change following cancer, rather than prospective designs to capture actual, measured changes in positive traits such as character strengths (i.e., character growth). This chapter discusses the challenges involved in examining post-traumatic growth in cancer patient populations and the advantages of incorporating a dyadic process approach as opposed to solely focusing on individual-level change. A dyadic process approach will permit examination of whether disclosure, support, empathy, and cognitive processing operate as mechanisms of character growth and will discuss the need for longitudinal data to fully examine post-traumatic growth as a dyadic outcome. To further elaborate on this dyadic approach, the authors propose an expanded theoretical model to delineate the intrapersonal and shared dyadic processes that underlie character and couple growth among cancer patients and caregivers.

Functional magnetic resonance imaging (fMRI) and magnetic resonance spectroscopy (MRS) studies provide an exciting opportunity to understand the neural substrates that underlie the pathophysiology of bipolar disorder. This chapter reviews fMRI and MRS meta-analyses from the past 10 years to examine whether meta-analytic results differ from those otherwise expected on the basis of individual studies considered in isolation. Across different meta-analytic studies, and predominantly consistent with extant fMRI hypotheses, the most replicated findings are an overactivity of amygdala, especially during emotional processing, and underactivity of right ventrolateral prefrontal cortex during emotional or cognitive processing in bipolar disorder. These functional abnormalities appear to present during mania or depression, but not during euthymia, suggesting they are related to mood state, symptom severity, or both. Additionally, they appear to be rather specific to bipolar disorder, as opposed to major depressive disorder or schizophrenia. Recent prospective studies also suggest that clinical improvement associates with normalization of functional abnormalities or functional connectivity between prefrontal cortex and amygdala. MRS meta-analyses, although more limited than fMRI, suggest elevated glutamate in prefrontal cortex and decreased N-acetylaspartate in the basal ganglia and hippocampus. Additional studies employing multimodal imaging or longitudinal designs could help to advance the understanding of these neurofunctional and neurochemical brain abnormalities and to develop better preventive and therapeutic strategies for this condition.

A cohort study is one in which the outcome (usually disease status) is ascertained for groups of individuals defined on the basis of their exposure. At the time exposure status is determined, all must be free of the disease. All eligible participants are then followed up over time. Since exposure status is determined before the occurrence of the outcome, a cohort study can clarify the temporal sequence between exposure and outcome, with minimal information bias. The historical and the population cohort study (Box 9.1) are efficient variants of the classical cohort study described above, which nevertheless retain the essential components of the cohort study design. The exposure can be dichotomous [i.e. exposed (to obstetric complications at birth) vs. not exposed], or graded as degrees of exposure (e.g. no recent life events, one to two life events, three or more life events). The use of grades of exposure strengthens the results of a cohort study by supporting or refuting the hypothesis that the incidence of the disease increases with increasing exposure to the risk factor; a so-called dose–response relationship. The essential features of a cohort study are: ♦ participants are defined by their exposure status rather than by outcome (as in case–control design); ♦ it is a longitudinal design: exposure status must be ascertained before outcome is known. The classical cohort study In a classical cohort study participants are selected for study on the basis of a single exposure of interest. This might be exposure to a relatively rare occupational exposure, such as ionizing radiation (through working in the nuclear power industry). Care must be taken in selecting the unexposed cohort; perhaps those working in similar industries, but without any exposure to radiation. The outcome in this case might be leukaemia. All those in the exposed and unexposed cohorts would need to be free of leukaemia (hence ‘at risk’) on recruitment into the study. The two cohorts would then be followed up for (say) 10 years and rates at which they develop leukaemia compared directly. Classical cohort studies are rare in psychiatric epidemiology. This may be in part because this type of study is especially suited to occupational exposures, which have previously been relatively little studied as causes of mental illness. However, this may change as the high prevalence of mental disorders in the workplace and their negative impact upon productivity are increasingly recognized. The UK Gulf War Study could be taken as one rather unusual example of the genre (Unwin et al. 1999). Health outcomes, including mental health status, were compared between those who were deployed in the Persian Gulf War in 1990–91, those who were later deployed in Bosnia, and an ‘era control group’ who were serving at the time of the Gulf war but were not deployed. There are two main variations on this classical cohort study design: they are popular as they can, depending on circumstances, be more efficient than the classical cohort design. The population cohort study In the classical cohort study, participants are selected on the basis of exposure, and the hypothesis relates to the effect of this single exposure on a health outcome. However, a large cohort or panel of subjects are sometimes recruited and followed up, often over many years, to study multiple exposures and outcomes. No separate comparison group is required as the comparison group is generally an unexposed sub-group of the panel. Examples include the British Doctor's Study in which over 30,000 British doctors were followed up for over 20 years to study the effects of smoking and other exposures on health (Doll et al. 1994), and the Framingham Heart Study, in which residents of a town in Massachusetts, USA have been followed up for 50 years to study risk factors for coronary heart disease (Wolf et al. 1988). The Whitehall and Whitehall II studies in the UK (Fuhrer et al. 1999; Stansfeld et al. 2002) were based again on an occupationally defined cohort, and have led to important findings concerning workplace conditions and both physical and psychiatric morbidity. Birth cohort studies, in which everyone born within a certain chronological interval are recruited, are another example of this type of study. In birth cohorts, participants are commonly followed up at intervals of 5–10 years. Many recent panel studies in the UK and elsewhere have been funded on condition that investigators archive the data for public access, in order that the dataset might be more fully exploited by the wider academic community. Population cohort studies can test multiple hypotheses, and are far more common than any other type of cohort study. The scope of the study can readily be extended to include mental health outcomes. Thus, both the British Doctor's Study (Doll et al. 2000) and the Framingham Heart Study (Seshadri et al. 2002) have gone on to report on aetiological factors for dementia and Alzheimer's Disease as the cohorts passed into the age groups most at risk for these disorders. A variant of the population cohort study is one in which those who are prevalent cases of the outcome of interest at baseline are also followed up effectively as a separate cohort in order (a) to study the natural history of the disorder by estimating its maintenance (or recovery) rate, and (b) studying risk factors for maintenance (non-recovery) over the follow-up period (Prince et al. 1998). Historical cohort studies In the classical cohort study outcome is ascertained prospectively. Thus, new cases are ascertained over a follow-up period, after the exposure status has been determined. However, it is possible to ascertain both outcome and exposure retrospectively. This variant is referred to as a historical cohort study (Fig. 9.1). A good example is the work of David Barker in testing his low birth weight hypothesis (Barker et al. 1990; Hales et al. 1991). Barker hypothesized that risk for midlife vascular and endocrine disorders would be determined to some extent by the ‘programming’ of the hypothalamo-pituitary axis through foetal growth in utero. Thus ‘small for dates’ babies would have higher blood pressure levels in adult life, and greater risk for type II diabetes (through insulin resistance). A prospective cohort study would have recruited participants at birth, when exposure (birth weight) would be recorded. They would then be followed up over four or five decades to examine the effect of birth weight on the development of hypertension and type II diabetes. Barker took the more elegant (and feasible) approach of identifying hospitals in the UK where several decades previously birth records were meticulously recorded. He then traced the babies as adults (where they still lived in the same area) and measured directly their status with respect to outcome. The ‘prospective’ element of such studies is that exposure was recorded well before outcome even though both were ascertained retrospectively with respect to the timing of the study. The historical cohort study has also proved useful in psychiatric epidemiology where it has been used in particular to test the neurodevelopmental hypothesis for schizophrenia (Jones et al. 1994; Isohanni et al. 2001). Jones et al. studied associations between adult-onset schizophrenia and childhood sociodemographic, neurodevelopmental, cognitive, and behavioural factors in the UK 1946 birth cohort; 5362 people born in the week 3–9 March 1946, and followed up intermittently since then. Subsequent onsets of schizophrenia were identified in three ways: (a) routine data: cohort members were linked to the register of the Mental Health Enquiry for England in which mental health service contacts between 1974 and 1986 were recorded; (b) cohort data: hospital and GP contacts (and the reasons for these contacts) were routinely reported at the intermittent resurveys of the cohort; (c) all cohort participants identified as possible cases of schizophrenia were given a detailed clinical interview (Present State examination) at age 36. Milestones of motor development were reached later in cases than in non-cases, particularly walking. Cases also had more speech problems than had noncases. Low educational test scores at ages 8,11, and 15 years were a risk factor. A preference for solitary play at ages 4 and 6 years predicted schizophrenia. A health visitor's rating of the mother as having below average mothering skills and understanding of her child at age 4 years was a predictor of schizophrenia in that child. Jones concluded ‘differences between children destined to develop schizophrenia as adults and the general population were found across a range of developmental domains. As with some other adult illnesses, the origins of schizophrenia may be found in early life’. Jones' findings were largely confirmed in a very similar historical cohort study in Finland (Isohanni et al. 2001); a 31 year follow-up of the 1966 North Finland birth cohort (n = 12,058). Onsets of schizophrenia were ascertained from a national hospital discharge register. The ages at learning to stand, walk and become potty-trained were each related to subsequent incidence of schizophrenia and other psychoses. Earlier milestones reduced, and later milestones increased, the risk in a linear manner. These developmental effects were not seen for non-psychotic outcomes. The findings support hypotheses regarding psychosis as having a developmental dimension with precursors apparent in early life. There are many conveniences to this approach for the contemporary investigator. ♦ The exposure data has already been collected for you. ♦ The follow-up period has already elapsed. ♦ The design maintains the essential feature of the cohort study, namely that information bias with respect to the assessment of the exposure should not be a problem. ♦ As with the Barker hypothesis example, historical cohort studies are particularly useful for investigating associations across the life course, when there is a long latency between hypothesized exposure and outcome. Despite these important advantages, such retrospective studies are often limited by reliance on historical data that was collected routinely for other purposes; often these data will be inaccurate or incomplete. Also information about possible confounders, such as smoking or diet, may be inadequate.