Confirmatory test of two factors and four subtypes of bipolar disorder based on lifetime psychiatric co-morbidity.

BACKGROUND: The first aim was to use confirmatory factor analysis (CFA) to test a hypothesis that two factors (internalizing and externalizing) account for lifetime co-morbid DSM-IV diagnoses among adults with bipolar I (BPI) disorder. The second aim was to use confirmatory latent class analysis (CLCA) to test the hypothesis that four clinical subtypes are detectible: pure BPI; BPI plus internalizing disorders only; BPI plus externalizing disorders only; and BPI plus internalizing and externalizing disorders. METHOD: A cohort of 699 multiplex BPI families was studied, ascertained and assessed (1998-2003) by the National Institute of Mental Health Genetics Initiative Bipolar Consortium: 1156 with BPI disorder (504 adult probands; 594 first-degree relatives; and 58 more distant relatives) and 563 first-degree relatives without BPI. Best-estimate consensus DSM-IV diagnoses were based on structured interviews, family history and medical records. MPLUS software was used for CFA and CLCA. RESULTS: The two-factor CFA model fit the data very well, and could not be improved by adding or removing paths. The four-class CLCA model fit better than exploratory LCA models or post-hoc-modified CLCA models. The two factors and four classes were associated with distinctive clinical course and severity variables, adjusted for proband gender. Co-morbidity, especially more than one internalizing and/or externalizing disorder, was associated with a more severe and complicated course of illness. The four classes demonstrated significant familial aggregation, adjusted for gender and age of relatives. CONCLUSIONS: The BPI two-factor and four-cluster hypotheses demonstrated substantial confirmatory support. These models may be useful for subtyping BPI disorders, predicting course of illness and refining the phenotype in genetic studies.

The relationship between cannabis involvement and suicidal thoughts and behaviors.

BACKGROUND: In the present study, we examined the relationship between cannabis involvement and suicidal ideation (SI), plan and attempt, differentiating the latter into planned and unplanned attempt, taking into account other substance involvement and psychopathology. METHODS: We used two community-based twin samples from the Australian Twin Registry, including 9583 individuals (58.5% female, aged between 27 and 40). The Semi-Structured Assessment of the Genetics of Alcoholism (SSAGA) was used to assess cannabis involvement which was categorized into: (0) no cannabis use (reference category); (1) cannabis use only; (2) 1-2 cannabis use disorder symptoms; (3) 3 or more symptoms. Separate multinomial logistic regression analyses were conducted for SI and suicide attempt with or without a plan. Twin analyses examined the genetic overlap between cannabis involvement and SI. RESULTS: All levels of cannabis involvement were related to SI, regardless of duration (odds ratios [ORs]=1.28-2.00, p<0.01). Cannabis use and endorsing ≥3 symptoms were associated with unplanned (SANP; ORs=1.95 and 2.51 respectively, p<0.05), but not planned suicide attempts (p>0.10). Associations persisted even after controlling for other psychiatric disorders and substance involvement. Overlapping genetic (rG=0.45) and environmental (rE=0.21) factors were responsible for the covariance between cannabis involvement and SI. CONCLUSIONS: Cannabis involvement is associated, albeit modestly, with SI and unplanned suicide attempts. Such attempts are difficult to prevent and their association with cannabis use and cannabis use disorder symptoms requires further study, including in different samples and with additional attention to confounders.

Suicide attempts in an adolescent female twin sample.

OBJECTIVE: To examine suicide attempts in an epidemiologically and genetically informative youth sample. METHOD: 3,416 Missouri female adolescent twins (85% participation rate) were interviewed from 1995 to 2000 with a telephone version of the Child Semi-Structured Assessment for the Genetics of Alcoholism, which includes a detailed suicidal behavior section. Mean age was 15.5 years at assessment. RESULTS: At least one suicide attempt was reported by 4.2% of the subjects. First suicide attempts were all made before age 18 (and at a mean age of 13.6). Major depressive disorder, alcohol dependence, childhood physical abuse, social phobia, conduct disorder, and African-American ethnicity were the factors most associated with a suicide attempt history. Suicide attempt liability was familial, with genetic and shared environmental influences together accounting for 35% to 75% of the variance in risk. The twin/cotwin suicide attempt odds ratio was 5.6 (95% confidence interval [CI] 1.75-17.8) for monozygotic twins and 4.0 (95% CI 1.1 -14.7) for dizygotic twins after controlling for other psychiatric risk factors. CONCLUSIONS: In women, the predisposition to attempt suicide seems usually to manifest itself first during adolescence. The data show that youth suicide attempts are familial and possibly influenced by genetic factors, even when controlling for other psychopathology.

A twin study of genetic and environmental influences on suicidality in men.

BACKGROUND: Previous studies that have examined genetic influences on suicidal behaviour were confounded by genetic vulnerability for psychiatric risk factors. The present study examines genetic influences on suicidality (i.e. suicidal ideation and/or suicide attempt) after controlling for the inheritance of psychiatric disorders. METHODS: Sociodemographics, combat exposure, lifetime DSM-III-R major depression, bipolar disorder, childhood conduct disorder, adult antisocial personality disorder, panic disorder, post-traumatic stress disorder, drug dependence, alcohol dependence and lifetime suicidal ideation and attempt were assessed in 3372 twin pairs from the Vietnam Era Twin Registry who were assessed in 1987 and 1992. Genetic risk factors for suicidality were examined in a multinomial logistic regression model. Additive genetic, shared environmental and non-shared environmental effects on suicidality were estimated using structural equation modelling, controlling for other risk factors. RESULTS: The prevalence of suicidal ideation and suicide attempt were 16.1% and 2.4% respectively. In a multinomial regression model, co-twin's suicidality, being white, unemployment, being other than married, medium combat exposure and psychiatric disorders were significant predictors for suicidal ideation. Co-twin's suicidality, unemployment, marital disruption, low education attainment and psychiatric disorders (except childhood conduct disorder) were significant predictors for suicide attempt. Model-fitting suggested that suicidal ideation was influenced by additive genetic (36%) and non-shared environmental (64%) effects, while suicide attempt was affected by additive genetic (17%), shared environmental (19%) and non-shared environmental (64%) effects. CONCLUSIONS: There may be a genetic susceptibility specific to both suicidal ideation and suicide attempt in men, which is not explained by the inheritance of common psychiatric disorders.