Manual: In a manual transmission, the problem is not so much the fluid degradation, but rather fluid contamination. This contamination occurs over time as the synchronizers, bearings and gears in the transmission wear out. The resulting metal particles then float around in the lubricant.
A lot of mental illnesses can have a genetic component, yes (eg. depression, bipolar disorder, anxiety, antisocial personality disorder, etc.).
To research the causes of Mental illness, consider researching the causes of these these diseases that may be similar, or associated with Mental illness: 1  Schizophrenia. 2  Personality disorder. 3  Post traumatic disorder.  Panic 1  attack. Generalised anxiety disorder.