The answer should be so obvious that there shouldn't be an article on it. But there it is.

Lake and Hurwitz, in Current Psychiatry, conclude that schizophrenia is really a subset of bipolar disorder.

The author's initial volley is (sentence 3):

The literature, including recent genetic data (1-6) marshals a persuasive argument that patients diagnosed with schizophrenia usually suffer from a psychotic bipolar disorder.

Well that's a pretty powerful assertion, supported by 6 different references. Except for one thing: none of the six references actually support that statement.

1. Berrettini: finds that of the various regions of the genome connected to bipolar disorder in genome scans, two are also found in scans of schizophrenia. Regions that overlap-- not genes, or collections of genes, but entire chunks of chromosomes. He says there are (perhaps) shared genetic susceptibilities, not that they are the same disease.
2. Belmaker: A review article. No new data.
3. Pope: specificity of the schizophrenic diagnosis-- written in 1978.
4. Lake and Hurwitz: says there's no such thing as schizoaffective disorder, which would be groundbreaking stuff if it weren't written by the same author as this article.
5. Post: Review article talking about kindling in affective disorders. In 1992.
6. DSM-IV. Seriously.

I'm game if you are: find the "persuasive argument" that these references "marshal" and then we have something to talk about.  What makes all this so hard to fathom is not the movement to lump the two disorders together, but rather to lump them together under the more arbitrary, heuristic diagnosis. It is schizophrenia, not bipolar, that actually has physical pathology. Let's review:

Brain anatomical findings:

• white-gray matter volumes decreased in caudate, putamen and nucleus accumbens. 1
• deficits in the left superior temporal gyrus and the left medial temporal lobe.2 3
• moderate volume reduction in the left mediodorsal thalamic nucleus (but total number of neurons and density of neurons is about the same) 4
• reduced gray matter volume, reduced frontotemporal volume, and increased volume of CSF in venticles 5 and 1

Physical features:

• Larger skull base and larger lower lip 1
• Velo-cardio-facial syndrome (22q11 deletion) 2
• vertical elongation of the face 3
• high arched palate 4

Granted, these aren't great; but try to find anything like this for bipolar.

Clearly, the Kool-Aid is delicious because they want us to drink it, too.

In the final section, magnificently entitled "What is standard of care?" the authors pronounce:

Antidepressants appear to be contraindicated, even in psychotic bipolar depressed patients.^14,15 We suggest that you taper and discontinue the initial antipsychotic when psychotic symptoms resolve.

Which is great, except it's not true. If the authors have some evidence that antidepressants actually increase the switch rate, I'd love to see it: but for sure references 14 and 15 aren't it. At least, could "contraindicated" be a tad overstated?
The last two sentences of the whole article:

The idea that “symptoms should be treated, not the diagnosis” is inaccurate and provides substandard care. When psychotic symptoms overwhelm and obscure bipolar symptoms, giving only antipsychotics is beyond standard of care.

No references given for these outrageous statements, but given the relevance of their previous references I guess it really doesn't matter. "Substandard care?" "Beyond the standard of care?" Really? I'll see you in court.