CNS diseases including depression have been treated with chemicals, typically unsuccessfully. This is big business and often questions challenging the status-quo are not entertained by the “money people.” It has been clear for a long time that chemicals are a bad way to treat the brain but just like anything else, confirmation and conformation biases drive research in universities and pharmaceutical companies. Both the diagnosis and the treatment of diseases affecting the brain including the most common ones such as pain and depression have always been inelegant and ineffective.
Humans, albeit carrying the same hardware across space and time, are different because of software, an outcome of experiences. Hence measurements that extract the combined effect of hardware and software often fail to diagnose properly. Perhaps it is time medicine moved away from archaic techniques like surveys for diagnosis and embrace mathematics better to tease out outcomes from multifactorial and complex systems.
More generally, it is unclear why any normal functioning human brain will not be depressed. Humans are given a hard time constraint and they are often subjected to catastrophic shocks to the brain, all through their life. It will be a miracle if those hysteresis loops not dull the brain as they stare at the impending end of life. The idea that correcting some chemical imbalances in the brain (a hardware treatment) will cure brain diseases is naive. Any brain disease has to be viewed as a spectrum and not a binary event, and if so, diagnosis and treatment modalities will be significantly different.
Medicine, a discipline of the body and not of the brain, has largely failed the latter. It will require a different way of looking at things.
(1) A chemical imbalance doesn’t explain depression. So what does? (sciencenews.org)