See Margaret Brown's discussion of Torrey in her Saybrook Graduate School dissertation. Other theories that claim mental illnesses are caused by social, political, economic, or other forms of oppression, stress and hardship merely shift the blame to vague, intangible, abstract forces that cannot be dealt with medically and scientifically. Many people endure such stresses without becoming mentally ill, and many people from comfortable circumstances do become mentally ill. There are studies showing the effects of social, political, and economic oppression on rates of mental disorders. Another contrasting advantage of the mental illness, medical, biogenetic, model is that it provides a legitimate basis for attracting treatment and research funding.
Tuberculosis is a disease.
So is depression.