Hoth et al dimensions of neuroticism and openness to experience. These effects were statistically significant, but were extremely subtle as exposure to early life stress accounted for only 2%–3% of the variance in the expression of the personality dimensions. This indicates that additional factors including other genes and/or environmental influences underlie the expression of these anxiety- related personality traits. However, we found no evidence for an interaction between COMT genotype and early life stress measured using a life events questionnaire. This may not be surprising, given that that the expression of psychological traits results from the interaction of multiple genes and environmental influences. The current study was limited by examining a single functional polymorphism in one gene rather then functional polymorphisms from multiple genes, which would provide a more realistic model. Some other studies have observed interaction effects between polymorphism variations in genes affecting dopamine neurotransmission and environmental exposure. Caspi and colleagues (2003) tested the moderating effects of variations in the serotonin transporter (5-HTT) gene on whether stressful experiences lead to depression in a prospective-longitudinal investigation. Analyses revealed that the serotonin transporter gene interacted with life events to predict depressive symptoms, diagnosis of depression, and suicidality. The authors discussed the fact that many candidate genes fail replication and account for little variation in the phenotype being examined. Differing levels of exposure to environmental risk may explain some of the mixed findings. 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