Final answer:
The gene allele associated with increased depressive symptoms in the context of stressful life events is the short allele of the serotonin transporter gene polymorphism (5-HTTLPR). This reflects a gene-environment interaction that influences the likelihood of developing depression.
Step-by-step explanation:
The gene allele associated with an increased prevalence of depressive symptoms when combined with stressful life events is the serotonin transporter gene polymorphism, specifically the short allele of the 5-HTT gene, known as 5-HTTLPR. Researchers have found that individuals with one or two copies of the short allele of the 5-HTTLPR gene have a higher likelihood of developing depression after experiencing stressful life events compared to individuals with two long alleles.
Influential studies by Caspi et al. (2003) and others have investigated the interaction between genetic predisposition—the 5-HTTLPR genotype—and environmental stressors, demonstrating that the presence of the short allele can modulate the impact of life stress on depression risk. This interaction suggests a gene-environment interaction where both genetic susceptibility and life experiences contribute to the development of depressive disorders.
It's important to note that the relationship between 5-HTTLPR, stress, and depression is complex, and possessing the short allele does not mean an individual will definitely develop depression. Other factors, such as additional genetic influences and personal resilience, also play significant roles in mental health.