Just FYI. Most mental health patients look 'normal'...they are people like you and me. They go to private psychiatrist visits with regular medication changes, if needed. Depression persists due to a chemical imbalance in brain, it's not 100% hereditary or genetic. Nor does it need to be permanent. There have been people who have made full recovery.
Clinical depression can occur due to some form of brain injury/disease (like it happened to Robin Williams), but rare. In his case, the suicide may be purely due to the fact that he knew he was going to be getting progressively worse.
From my experience, I have found that prolonged sadness leading to depression has a lot of social triggers...for example, a teen showing anorexia tendencies and feeling shunned in high school. I see depression more as a symptom of a holistic issue. It is not a disease like we say someone has a viral infection or cancer. A lot of times people don't kill themselves due to depression, but do so due to social isolation or feeling victimized, persistent bullying, grieving or some life event that makes them feel helpless/unable to seek help. Most likely, he was battling this issue and considering suicide a long time, before he actually did it. The fact that he got separated from his core friend circle (and had limited contact with his family) who knew him inside and out for years, made him very vulnerable when facing a difficult life issue (only he knows what it was).
People who bounce back easily from depressive episodes have good social support systems. Most people when given hope, consistent support and positive encouragement, do quite well.
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