Reading through the paper by Liz Forty and colleagues  (open-access) it appears that a similar scenario might also pertain to other behaviourally-defined conditions as per the example of bipolar disorder (BD) and their conclusion: "Bipolar disorder is associated with high rates of medical illness."
|If I had a world of my own, everything would be nonsense|
The Forty paper is open-access but a few pointers might be useful...
- Based on quite an impressive participant number (N=1720) diagnosed with bipolar disorder, lifetime rates of self-reported medical illnesses were compared with data derived from participants diagnosed with unipolar depression (N=1737) and asymptomatic controls (N=1340) (both previously described in other work from some of the authors ).
- Participants were quizzed - yes, no or uncertain - over whether any of 20 health conditions had been diagnosed by a health professional including: "asthma, cancer, diabetes type 1, diabetes type 2, elevated lipids/high cholesterol, epilepsy, gastric ulcers, heart disease, hypertension, kidney disease, liver disease, memory loss/dementia, migraine headaches, multiple sclerosis, osteoarthritis, osteoporosis, Parkinson’s disease, rheumatoid arthritis, stroke, thyroid disease." All the 'uncertain' codings were "excluded from analyses for that medical illness".
- Results: "The most prevalent medical conditions in the bipolar sample were migraine headache (23.7%), asthma (19.2%), elevated lipids (19.2%), hypertension (15%), thyroid disease (12.9%) and osteoarthritis (10.8%)." Quite a few of these conditions were significantly more frequently reported in cases of BD over control groups (see Figure 1 here). I'll in particular highlight the findings for asthma and thyroid disease as being more commonly reported in the BD group.
- Authors also divided the BD group up into subgroups (BD1 and BD2) based on the severity of manic episodes, and reported that: "The rates of gastric ulcers, heart disease, Parkinson’s disease and rheumatoid arthritis were significantly higher in the bipolar II group." They also found that several variables seemed to be linked to an increased medical illness burden including: "a longer illness duration, a typically acute onset of mood episodes, a greater number of psychiatric in-patient admissions, deterioration in functioning, increased rates of anxiety disorder, suicide attempt, rapid cycling, and treatment with anxiolytics, mood stabilisers and electroconvulsive therapy (ECT)." Some of these variables also predicted the high medical illness burden group too.
Reiterating the authors' sentiments about the need for such medical comorbidity to be taken into account by healthcare professionals "in order to improve outcomes for patients with bipolar disorder" these are important results. Assuming that there may be shared/overlapping genetic or biological mechanisms at work which influence risk of BD and also such medical comorbidity, one might think that future work would take this into account when looking at the possible underlying aetiology of BD. Such work might also accept the heterogeneity noted in BD as per similar sentiments when it comes to conditions like 'the autisms' (see here) and 'the schizophrenias' (see here).
Asthma has been highlighted from the Forty results on the basis of the condition already showing something of an interesting 'link' with conditions like autism and attention-deficit hyperactivity disorder, ADHD (see here). Indeed, data from Taiwan (yes, further interrogation of the Taiwan National Health Insurance Research Database) concluded that a diagnosis of asthma might increase the risk of subsequent mood disorders (including BD) later in life . Forty et al suggested that of the possible reasons why asthma might be more frequently present in BD "carbon dioxide hypersensitivity and corticosteroid therapy may partly explain this association." I'd be perhaps inclined to add that other [speculative] work looking at the link between autism and asthma for example, might also offer another potential explanation .
Thyroid disease was also plucked out from the Forty data. The reason: some interesting data previously covered on this blog talking about autoimmune thyroiditis and various types of depression (see here). I'm not by the way saying that every case of thyroid disease in BD is due to such an autoimmune pathology, but as per other discussions, there might be quite a bit more to see when it comes to immune system function and behavioural and/or psychiatric diagnoses. At the very least, testing for said autoimmune issues might be considered for some.
There is little more for me to say on this subject matter. This is by no means the first time that medical comorbidity has been linked to BD  and even more widely depression  and I very much doubt it will be the last. If there are lessons to be learned from this area of investigation, the primary one must be to look at mind and body when it comes to diagnosing and managing psychiatric issues such as bipolar disorder as per other examples.
Oh, and I wonder if this would be a good time to introduce the findings from Almeida and colleagues  again published in the same journal as Forty and colleagues, concluding: "B vitamins did not increase the 12-week efficacy of antidepressant treatment, but enhanced and sustained antidepressant response over 1 year." Food for thought?
Music: Janis Joplin and Piece of my heart.
 Forty L. et al. Comorbid medical illness in bipolar disorder. Br J Psychiatry. 2014. October 30.
 Crawford MJ. et al. Assessment and treatment of physical health problems among people with schizophrenia: national cross-sectional study. Br J Psychiatry. 2014. October 16.
 Farmer A. et al. Medical disorders in people with recurrent depression. Br J Psychiatry. 2008 May;192(5):351-5.
 Chen MH. et al. Higher risk of developing major depression and bipolar disorder in later life among adolescents with asthma: a nationwide prospective study. J Psychiatr Res. 2014 Feb;49:25-30.
 Becker KG. Autism, asthma, inflammation, and the hygiene hypothesis. Med Hypotheses. 2007;69(4):731-40.
 Sylvia LG. et al. Medical burden in bipolar disorder: findings from the Clinical and Health Outcomes Initiative in Comparative Effectiveness for Bipolar Disorder study (Bipolar CHOICE). Bipolar Disord. 2014 Aug 16. doi: 10.1111/bdi.12243.
 Smith DJ. et al. Depression and multimorbidity: a cross-sectional study of 1,751,841 patients in primary care. J Clin Psychiatry. 2014 Nov;75(11):1202-1208.
 Almedia OP. et al. B vitamins to enhance treatment response to antidepressants in middle-aged and older adults: results from the B-VITAGE randomised, double-blind, placebo-controlled trial. Br J Psychiatry. 2014. September 25.
Forty L, Ulanova A, Jones L, Jones I, Gordon-Smith K, Fraser C, Farmer A, McGuffin P, Lewis CM, Hosang GM, Rivera M, & Craddock N (2014). Comorbid medical illness in bipolar disorder. The British journal of psychiatry : the journal of mental science PMID: 25359927