40% of mental illness precursors can be diagnosed as early as 14 and 75% by age 25.
Many other mental issues as well.
Parkinsons for instance starts many years before any symptoms happen.
I was depressed as a teen, Started around 13 or 14. I just taught myself not to act on my impulses. I have been paranoid my whole life also, again I just taught myself not to act on beliefs that I could not confirm. Of course since I believe them that is not always an easy task. And if I am sick or overly tired it gets even harder.
My Navy Doctor told me that I should never have made it through Boot Camp much less get promoted to GySgt and last 16 years. That's how bad it is. I suffer recurring Major Depression, constant depression in between major episodes, I have paranoid delusional personality and Paranoid delusional disorder.
I believe the final straw that broke my act was the death of my Mother. I never talked to anyone about my problems but always knew if I had to I could talk to her. When she died that option was gone and within 2 years I had a break down.
Fortunately for me a MSgt that I worked with had a break down and had me drive him to the Hospital. That happened about a month before i broke down. His willingness to ask for help was enough to stop me from killing myself and asking for help myself. It was still touch and go, I had the weapon and had a plan. But decided I would see if they could help.
It ended my career and I have had some tough years finding the right meds. There were days I just laid in bed not moving cause if I did I would shoot myself. I was in and out of the Hospital 2 or 3 times a year from 1996 to 1999.
I finally ask for disability and that was enough that I survived until 2004 when we found a combination of meds that actually helped.
I am still depressed but it is manageable. I very seldom have a plan though I still would prefer to be dead. And I have not been in the hospital since 2002.