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.).
One in four people will be affected by mental illness. Sky News reports that, five of the most common psychiatric disorders are genetically linked.. This news is based on a landmark study that examined the genetic sequences of more than 50,000 people. This useful and well-conducted study provides an invaluable insight into the possible genetic factors linked to these common mental health disorders.