Dheeraj Rai

Epilepsy and psychiatric comorbidity: a nationally representative population-based study

Purpose:  In a nationally representative population‐based study in England, we estimated the burden of psychiatric and neurodevelopmental comorbidities in people with epilepsy. We investigated whether any overrepresentation of comorbidities could be explained by epilepsy being a chronic medical or neurologic condition, or by the confounding effect of demographic and socioeconomic factors or other health conditions.

Country- and individual-level socioeconomic determinants of depression: multilevel cross national comparison

BACKGROUND The prevalence and correlates of depression vary across countries. Contextual factors such as country-level income or income inequalities have been hypothesised to contribute to these differences. AIMS To investigate associations of depression with socioeconomic factors at the country level (income inequality, gross national income) and individual (education, employment, assets and spending) level, and to investigate their relative contribution in explaining the cross-national variation in the prevalence of depression. METHOD Multilevel study using interview data of 187 496 individuals from 53 countries participating in the World Health Organization World Health Surveys. RESULTS Depression prevalence varied between 0.4 and 15.7% across countries. Individual-level factors were responsible for 86.5% of this variance but there was also reasonable variation at the country level (13.5%), which appeared to increase with decreasing economic development of countries. Gross national income or country-level income inequality had no association with depression. At the individual level, fewer material assets, lower education, female gender, economic inactivity and being divorced or widowed were associated with increased odds of depression. Greater household spending, unlike material assets, was associated with increasing odds of depression (adjusted analysis). CONCLUSIONS The variance of depression prevalence attributable to country-level factors seemed to increase with decreasing economic development of countries. However, country-level income inequality or gross national income explained little of this variation, and individual-level factors appeared more important than contextual factors as determinants of depression. The divergent relationship of assets and spending with depression emphasise that different socioeconomic measures are not interchangeable in their associations with depression.

Psychological distress and risk of long-term disability: population-based longitudinal study

Background Common mental disorders are known to cause long-term disability, although not much is known about long-term consequences of milder forms of psychological distress. Objective To investigate the association between increasing levels of psychological distress and 5-year risk of long-term disability pensions awarded for somatic or psychiatric conditions. Methods In this longitudinal population-based study, a cohort of 17 205 individuals, aged 18–64 years, recruited in 2002 in Stockholm County was prospectively followed up for new disability pension awards. The 12-item General Health Questionnaire (GHQ-12) was used to measure baseline psychological distress, and participants were categorised as having no, mild, moderate or severe psychological distress (GHQ-12 scores of 0; 1–2; 3–7 and 8–12, respectively). Details of new disability pension awards were obtained through record linkage with the Swedish National Insurance register. Comprehensive information on a range of sociodemographic, lifestyle and health characteristics was available. Results Increasing levels of psychological distress at baseline were associated with an increased likelihood of obtaining a disability pension later in life. Even mild psychological distress was independently associated with the award of a disability pension for both somatic (HR=1.7; 95% CI 1.3 to 2.2) and psychiatric diagnoses (2.2; 1.4 to 3.6). Over a quarter of disability pensions awarded for a somatic diagnosis, and almost two-thirds awarded for a psychiatric diagnosis, could be attributed to psychological distress. Conclusions Mild psychological distress may be associated with more long-term disability than previously acknowledged and its public health importance may be underestimated.

Common mental disorders, subthreshold symptoms and disability: longitudinal study

In a representative sample of the UK population we found that common mental disorders (as a group and in ICD-10 diagnostic categories) and subthreshold psychiatric symptoms at baseline were both independently associated with new-onset functional disability and significant days lost from work at 18-month follow-up. Subthreshold symptoms contributed to almost half the aggregate burden of functional disability and over 32 million days lost from work in the year preceding the study. Leaving these symptoms unaccounted for in surveys may lead to gross underestimation of disability related to psychiatric morbidity.

Brief Report: Maternal Smoking during Pregnancy and Autism Spectrum Disorders.

Prenatal exposure to tobacco smoke is suggested as a potential risk factor for autism spectrum disorders (ASD). Previous epidemiological studies of this topic have yielded mixed findings. We performed a case–control study of 3,958 ASD cases and 38,983 controls nested in a large register-based cohort in Sweden. ASD case status was measured using a multisource case ascertainment system. In adjusted results, we found that maternal smoking during pregnancy is not associated with increased risk of ASD regardless of presence or absence of comorbid intellectual disability. Apparent associations were attributable to confounding by sociodemographic characteristics of parents such as education, income, and occupation.

Evidence of Common Genetic Overlap Between Schizophrenia and Cognition

Cognitive impairment is a core feature of schizophrenia but there is limited understanding of the genetic relationship between cognition in the general population and schizophrenia. We examine how common variants associated with schizophrenia en masse contribute to childhood cognitive ability in a population-based sample, and the extent to which common genetic variants associated with childhood cognition explain variation in schizophrenia. Schizophrenia polygenic risk scores were derived from the Psychiatric Genomics Consortium (n = 69 516) and tested for association with IQ, attention, processing speed, working memory, problem solving, and social cognition in over 5000 children aged 8 from the Avon Longitudinal Study of Parents and Children birth cohort. Polygenic scores for these cognitive domains were tested for association with schizophrenia in a large UK schizophrenia sample (n = 11 853). Bivariate genome-wide complex trait analysis (GCTA) estimated the amount of shared genetic factors between schizophrenia and cognitive domains. Schizophrenia polygenic risk score was associated with lower performance IQ (P = .001) and lower full IQ (P = .013). Polygenic score for performance IQ was associated with increased risk for schizophrenia (P = 3.56E-04). Bivariate GCTA revealed moderate genetic correlation between schizophrenia and both performance IQ (r G = −.379, P = 6.62E-05) and full IQ (r G = −.202, P = 5.00E-03), with approximately 14% of the genetic component of schizophrenia shared with that for performance IQ. Our results support the presence of shared common genetic factors between schizophrenia and childhood cognitive ability. We observe a genetic relationship between schizophrenia and performance IQ but not verbal IQ or other cognitive variables, which may have implications for studies utilizing cognitive endophenotypes for psychosis.

Risks for Nonaffective Psychotic Disorder and Bipolar Disorder in Young People With Autism Spectrum Disorder: A Population-Based Study

IMPORTANCE Whether individuals with autism spectrum disorder (ASD) are at increased risk for nonaffective psychotic disorder (NAPD) or bipolar disorder (BD) is unknown. OBJECTIVE To test whether the risks for NAPD and BD in individuals with ASD are increased and whether these risks are higher than those of their siblings not diagnosed as having ASD. DESIGN, SETTING, AND PARTICIPANTS We performed a nested case-control study of all individuals 17 years or younger who ever resided in Stockholm County, Sweden, from January 1, 2001, through December 31, 2011 (Stockholm Youth Cohort). We included cohort members ever diagnosed as having ASD (n = 9062) and their full siblings never diagnosed as having ASD. Each case was matched with 10 control individuals of the same sex born during the same month and year. Using Swedish registers, cases, siblings, and controls were followed up until December 31, 2011. By then, the oldest individuals had reached the age of 27 years. EXPOSURES Autism spectrum disorder, registered before age 16 or 28 years. We distinguished between ASD with and without intellectual disability (ID). MAIN OUTCOMES AND MEASURES We calculated odds ratios (ORs) for NAPD and BD adjusted for age, sex, population density of place of birth, personal or parental history of migration, hearing impairment, parental age, parental income, parental educational level, and parental history of psychiatric disorder. RESULTS The adjusted ORs for NAPD and BD for cases with non-ID ASD registered before age 16 years were 5.6 (95% CI, 3.3-8.5) and 5.8 (95% CI, 3.9-8.7), respectively; the adjusted ORs for cases with ID ASD were 3.5 (95% CI, 2.0-6.0) and 1.8 (95% CI, 0.8-4.1). The adjusted ORs for NAPD and BD in cases with non-ID ASD registered before age 28 years were 12.3 (95% CI, 9.5-15.9) and 8.5 (95% CI, 6.5-11.2), respectively; for cases with ID ASD, these ORs were 6.4 (95% CI, 4.2-9.8) and 2.0 (95% CI, 1.0-3.9), respectively. The ORs for NAPD and BD for the nonautistic full siblings of cases for whom ASD was registered before age 16 years, adjusted for hearing loss, were 1.8 (95% CI, 1.1-2.7) and 1.7 (95% CI, 1.1-2.6), respectively. CONCLUSIONS AND RELEVANCE A diagnosis of ASD is associated with a substantially increased risk for NAPD and BD. This finding contributes to our understanding of these disorders and has implications for the management of ASD.

Physical ill health, disability, dependence and depression: Results from the 2007 national survey of psychiatric morbidity among adults in England

BACKGROUND The relationship between physical ill health, disability, and depression is not straightforward. Both cross-sectional and longitudinal studies have clearly shown that medical illness and physical disability are strongly associated with depression. OBJECTIVE To test the hypothesis that disability is associated with an increased prevalence of depression irrespective of physical health problems and that this is proportionate to the severity of disability (measured in terms of the number of difficulties in daily activities and the degree of dependence on others). METHODS Using a random probability sample design, 7460 respondents were interviewed for the third national survey of psychiatric morbidity of adults in the private household population in England. Fieldwork was carried out throughout 2007. The prevalence of depression was established by the administration of the revised Clinical Interview Schedule (CIS-R), while disability was measured by reported difficulties in activities of daily living (ADL) and instrumental activities of daily living (IADL). RESULTS Disability was associated with depression even after adjustment for physical ill health. The number of ADL/IADL difficulties was directly related to the likelihood of respondents having depression. Dependence on others was not associated with depression once severity of disability had been accounted for. CONCLUSION All ADL/IADL limitations are significantly associated with depression and there seems to be a cumulative effect irrespective of whether the limitation is in personal care or in instrumental activities such as mobility problems.

The relationship between happiness and intelligent quotient: the contribution of socio-economic and clinical factors

BACKGROUND Happiness and higher intelligent quotient (IQ) are independently related to positive health outcomes. However, there are inconsistent reports about the relationship between IQ and happiness. The aim was to examine the association between IQ and happiness and whether it is mediated by social and clinical factors. Method The authors analysed data from the 2007 Adult Psychiatric Morbidity Survey in England. The participants were adults aged 16 years or over, living in private households in 2007. Data from 6870 participants were included in the study. Happiness was measured using a validated question on a three-point scale. Verbal IQ was estimated using the National Adult Reading Test and both categorical and continuous IQ was analysed. RESULTS Happiness is significantly associated with IQ. Those in the lowest IQ range (70-99) reported the lowest levels of happiness compared with the highest IQ group (120-129). Mediation analysis using the continuous IQ variable found dependency in activities of daily living, income, health and neurotic symptoms were strong mediators of the relationship, as they reduced the association between happiness and IQ by 50%. CONCLUSIONS Those with lower IQ are less happy than those with higher IQ. Interventions that target modifiable variables such as income (e.g. through enhancing education and employment opportunities) and neurotic symptoms (e.g. through better detection of mental health problems) may improve levels of happiness in the lower IQ groups.

Sleep disturbances and depressive symptoms: an investigation of their longitudinal association in a representative sample of the UK general population

BACKGROUND It has been argued that sleep disturbances are a risk factor for depression but previous longitudinal studies have had limitations and not addressed alternative explanations. The aim of this study was to examine the longitudinal association between sleep disturbances and depressive symptoms in a nationally representative sample. METHOD Data from the 18-month follow-up of the UK National Psychiatric Morbidity survey were used (n = 2406). Sleep disturbances, depressive and other psychiatric symptoms (fatigue, concentration problems, irritability, anxiety and pain symptoms) were assessed using the Revised Clinical Interview Schedule (CIS-R). The bidirectional association between symptoms was investigated with logistic regression analyses and path analysis. RESULTS Sleep disturbances and depressive symptoms were correlated with each other cross-sectionally (r = 0.52, p < 0.001). In the longitudinal analysis, sleep disturbances at baseline did not predict depressive symptoms at follow-up [odds ratio (OR) 1.27, 95% confidence interval (CI) 0.51-3.19] and the same was observed for the reciprocal association (OR 0.87, 95% CI 0.56-1.35). In the path analysis, the reciprocal model did not have a better fit compared to the simpler first-order model without cross-lagged paths. The path from sleep disturbances at baseline to depressive symptoms at follow-up had a minimal contribution to the explained variance of the latter (<1%). CONCLUSIONS Previous studies may have overestimated the importance of sleep disturbances as an independent risk factor of depression. The strong cross-sectional association is compatible with sleep disturbances being either a prodromal or a residual symptom of depression and this may have implications for recognition and treatment of depression.