A biological theorist studies a psychological disorder through the interconnectivity of an entire network of brain structures. This shows the recent belief that the key to psychological disorders lies in:

Hormonal Imbalances generated by irregular stimulus or impulses of brain

Explanation:

According to the recent research, most of the patients with serious psychological disorders have severe imbalances of hormones in their body. Most of them also have a history of trauma to head and spine. When a part of brain gets damaged, it may become dead (under-active) or may become overactive and hormonal instability have serious psychological complications.