Final answer:
Having a family history of major depressive disorder increases the risk of developing depression by a factor of 3 to 5, emphasizing the role of genetic factors and environmental influences in the disorder.
Step-by-step explanation:
Having one or more parents with major depressive disorder increases one's risk of developing the disorder by a factor of 3 to 5. This indicates that genetic factors play a significant role in the susceptibility of individuals to major depressive disorders, alongside environmental influences.
Studies such as those by Biederman et al. (2001) show patterns of psychopathology in children of parents with major depressive disorder. Likewise, the quoted statistics on the increased likelihood of adoptees with high genetic risk developing schizophrenia in disturbed environments versus healthy environments underscore the impact of the combination of genetic predisposition and environmental factors on mental health outcomes.
Therefore, when considering the multifactorial nature of depression, it's evident that having a family history of the condition is a significant risk factor, which is further modified by life experiences and external stressors.