Social phobia in a population-based female adolescent twin sample: co-morbidity and associated suicide-related symptoms

BACKGROUND: This report attempted to replicate and extend prior work examining social phobia (SP), co-morbid psychiatric illnesses, and the risk of suicidal ideation and suicide attempts incurred by their adolescent sufferers. METHODS: SP, alcohol dependence (ALD) and major depressive disorder (MDD) diagnoses, and suicide-related symptoms, were assessed in a population-based adolescent female twin sample. The differentiation of risks as a function of co-morbidity was explored. A trivariate model was fitted to estimate sharing of genetic and environmental vulnerability between SP and co-morbid disorders. RESULTS: The lifetime prevalence of SP was 16.3 %. Significant risk for co-morbid MDD (OR = 3.2) and ALD (OR = 2.1) was observed. Strong evidence for shared genetic vulnerability between SP and MDD (respective heritabilities 28%, 45%; genetic r = 1.0) was observed with moderate support noted for similar sharing between SP and ALD (genetic r = 0.52, heritability for ALD 63%). SP with co-morbid MDD was associated with elevated risk for ALD and for suicide-related symptoms. CONCLUSIONS: SP is a common illness often followed by co-morbid MDD and ALD. SP with comorbid MDD predicts a substantially elevated risk of ALD and suicide-related symptoms, stressing the need for early SP detection.