Antidepressants commonly cause suicide by treating the physical retardation symptoms of depression before treating mood symptoms. If someone is so depressed they can't get out of bed, then starts taking an antidepressant, they might continue to be just as depressed, but now have the energy to get out of bed. This is especially common with teens.

SSRIs definitely do work for some people, but the mechanism isn't well understood and is well-researched. There is plenty of actual scientific evidence to back up the serotonin imbalance hypothesis, but of course no amount of evidence can ever prove a theory true. There are other findings that indicate other theories -- my personal favorite is that the antidepressant effect of SSRIs is from incidental neurogenesis, and NSI-189 looks promising as the first of hopefully many antidepressant drugs coming from this theoretical basis entirely.

While a lot of people who commit suicide are being treated for a mental illness, the majority of people who complete suicide (i.e., actually kill themselves) are not in any sort of treatment. Suicide is actually a very impulsive behavior in most cases. For this reason, if you make the means of suicide less available (putting fences up on bridges, gun control, etc.), you actually decrease the incidence of suicide even though there are plenty of ways people can kill themselves.

A few nits to your post:

* Psychiatry isn't based on a chemical imbalance hypothesis. SSRIs, and some other drugs, are. Psychiatry as a whole is far too wide to be based on any particular theory, except maybe probabilistic determinism (the assumption that events have causes that can be used to predict the future).

* Psychiatrists are medical doctors with a specialty in mental health. "Psychiatry" is not a very well-defined area, and usually indicates the speaker is a Scientology crank. The actual field you discuss in your post is psycho-pharmacology. You don't comment at all on diagnostic procedures, which is a major non-pharmocological component of a psychiatrist's job, nor on non-pharmocological therapies, some of which have been very well-studied and indicate to the best of our scientific ability to be reliably positive mental health interventions.

As a final note, it wouldn't surprise me if all of the Valley, and indeed most of the world, was on "meds" of some kind. Most people drink. A lot of people smoke. Marijuana is legal in California and is going to be legal soon in the general case. Video games exist that are thin wrappers around psychological reward pathways, and are functionally equivalent to drugs, even if they don't involve ingesting or inhaling anything. There are very few "pure" humans. The question isn't whether or not someone is "on meds," but whether they're getting what they need as a person to self-actualize.

PS: I recognize I have made a number of factual claims in this post. I have not included any links to scientific papers because it took long enough to type out and I didn't want to spend twice as long digging through sources. I'll provide the papers I thought of while writing this, but only under one condition: anyone asking for them shows convincing (to me) evidence that they have looked for these sources on their own. I help those who help themselves.