Bipolar Disorder. What are we really talking about?

As a clinical psychiatrist, I have a lot of thoughts about studies, genetic or otherwise, of the various mental disorders.  Before we even look at the merits of a genetic association study for a particular mental disorder, I think it's worth looking at a few diagnoses and some of the possible pitfalls of doing a study specific to a diagnosis.  Some diagnoses might have a more "organic" flavor to them (Schizophrenia, Schizoaffective Disorder, Bipolar Disorder) and one might assume that they would lend themselves better to genetic association study.  So I'll start with one of those: Bipolar Disorder.

I worked largely in acute psychiatric settings for most of my career.  Few things are more interesting than having a floridly manic patient (literally) dragged into your crisis center.  The person will often be speaking at a breathtaking pace, speedily rhyming and making up words, smiling from ear to ear, telling you they are a billionaire and engaged to this or that celebrity, whom they can speak with telepathically, all this while they haven't slept in days, but appear more energetic than I've ever been in my life.  Conversely, they might have a severe depressive episode, where they lay in bed for weeks at a time, believe the devil is speaking to them, stop eating, etc.
That sounds quite organic, rather similar to the effects of drugs like amphetamine derivatives and cocaine when manic or perhaps downers like quaaludes and valium when they are having a depressive episode.  Of course, it's plausible that there is some organic/genetic component involved.  So why do I almost instantly assume that any study purporting to show genetic linkages to Bipolar Disorder is bogus before I've even looked at the study?  Because I know from experience that a large chunk of the patients in such a study don't really have Bipolar Disorder.  People are given the diagnosis of Bipolar Disorder who have never had any kind of experiences like the ones I described above.  Part of this has to do with the type of people who control academia and the DSM (Diagnostic and Statistical Manual).  They want to get their names in print, run big "Bipolar Disorder Clinics",  hang out with other "elites."  I'm sure you know the type.  What they generally lack, is any clinical acumen.  They are like pilots in white gloves.  Their understanding of mental illness is based on things they've read from others just like them.  They generally have little interest in probing the depths of the human mind and would consider such things as psychopathology.  This creates a problem in terms of diagnosis in a number of ways.
The first is, in my view, semantics.  We have a limited language to describe psychological symptoms (largely I'm talking about English, here, but I imagine it is similar in most other modern languages).  Huston Smith once said, "For every psychological term in English, there are four in Greek and forty in Sanskrit."  (Sanskrit, by the way, is a rather beautiful psycho-spiritual language and is worth reading about in its own right).  So when we simplify a manic episode as being "up" and "cycling up and down," we are giving a very limited description of what is really going on.  Then we have a patient who tells us that they are "up" sometimes and "down" others and they "cycle back and forth."  These vague symptoms can be attributed to a variety of mental issues, but our "leaders in the field" will hear that description and decide it is similar to the descriptions given by actual manic and severely depressed patients.  What this has led to are attenuated diagnoses like "Bipolar II Disorder" and "Cyclothymic Disorder", suggesting a continuum of severity from these disorders to Bipolar I Disorder".  In my experience, nothing could be further from the truth.  These are unrelated problems and once the patient gets labeled as "Bipolar", The Bipolar "II"seems to fade away.  These patients will significantly outnumber patients with actual Bipolar I symptoms and for reasons I'll discuss shortly, will be all too happy to participate in studies related to Bipolar Disorder.
Financial incentives play a big role in this.  In order for a psychiatrist to be paid from insurance companies (private or government), they need to be treating a disorder that is in the DSM (we are now on DSM 5).  Some disorders are considered more severe and more worthy of remuneration.  One of these is Bipolar Disorder.  This is more lucrative than what are called "personality disorders," or substance abuse issues, for example, so both the doctor and the patient are motivated to give the diagnosis of Bipolar Disorder.  It might be obvious why the doctor is motivated (financially) to give the diagnosis, but you might wonder what is in it for the patient?
This is where a personality disorder called Borderline Personality Disorder clouds the clinical picture.  I won't go into great detail about this diagnosis, but briefly, it involves patients who generally had some severe childhood trauma (sexual abuse or physical abuse) and have a very hard time modulating their moods, tend to be preoccupied with harming themselves and get themselves into relationship and substance abuse problems to a significant degree.  Few people want to be diagnosed with a "personality disorder" and it satisfies an urge for identity and justifies certain behaviors if the person can get a "nicer" diagnosis like Bipolar Disorder.  You will find "borderlines" working their way into all manner of psychiatric studies, likely throwing off the results, although they are usually good actors in reporting symptoms that the evaluators want to hear.
Patients with substance abuse issues also are often happy to receive a diagnosis of Bipolar Disorder, as are their doctors, as this is a way for them to justify their substance abuse as "self-medication."  Substance abuse doesn't pay psychiatrists very well.
Lastly, we have the almighty pharmaceutical industries.  Medications have to be tied to specific diagnoses in order to be covered by insurers.  This is a multibillion dollar industry.  There is a lot of incentive for certain diagnoses to be given.  One way or another, a lot of people are going to be given this diagnosis that don't really have it, in my opinion.
This isn't all just a "hunch" on my part, by the way.  Psychiatrists are fully aware of when their patients are participating in studies.  In my experience, a lot of the patients participating in these studies don't have Bipolar Disorder in the classic sense, so any study that shows an association between Bipolar Disorder and a particular gene is,  almost certainly producing a false positive before we even get to the point of assessing the merits of the study.