IMO the chemical imbalance theory was invented as a marketing ploy for advertising medications.

It's not so much as a chemical imbalance as it is a problem with disordered neuronal processing and synaptic pruning at accelerated rates during adolescence.

It's a great marketing ploy to describe in the most simplistic terms for consumers who use these drugs. It doesn't help that most psychiatrists don't have time and just use verbatim what their marketing reps told them. You'd be lucky to find a psychiatrist who would take the time to talk to you more than 5 minutes, so saying "it's a chemical imbalance" is the shortest and easiest way to explain to the average consumer why using drugs can "help".

We are still in the dark ages of psychiatry. We have made little progress over the last 50 years. 49 years ago was the last prefrontal lobotomy performed in America. We still use the same drugs to treat bipolar that was discovered in the mid 1800's (Lithium) and we don't have any other medication specific for bipolar disorder. All medications are 'borrowed' from treatments for epilepsy, depression, or schizophrenia.

However new discoveries are being found each day. Like how ketamine can successfully treat severe depression for bipolar without causing mania (like antidepressants do).

With Neuropsychiatry there is a lot of new information to be discovered. It's still in it's infancy and there is so much to discover about the human brain. This is why we need to push our governments to support the health sciences.

I'm gonna stop babbling. Sorry for the rant, this is something I feel very personal about.