Medical Comorbidity in Bipolar Disorder, II: The ‘Why’ Behind the ‘What’

Posted on July 9, 2012 by

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In our last post, Medical Comorbidity in Bipolar Disorder: Just the (Unpleasant) Facts), a guest post on Madam Bipolar, an innovative site dedicated solely to issues surrounding the illness, we addressed the upsettingly high correlation between bipolar disorder (BD) and physical illnesses.

We covered studies that found that people with BD had increased likelihoods of contracting conditions spanning every organ system, that rates of chronic fatigue syndrome, migraine, asthma, chronic bronchitis, multiple chemical sensitivites, hypertension, and gastric ulcer were “significantly higher” among BD sufferers than controls, and even one on BD patients with co-occurring substance abuse issues that found that  every single patient enrolled in the study had at least one medical illness. And, to strain credulity more, on average the subjects had 4.9 different medical conditions.

But the facts on the ground beg the question: WHY are those with BD prone to co-occurring (“comorbid”) medical problems in such high numbers? It certainly can’t be just a matter of happenstance.
And indeed it isn’t.

There are two separate issues, really, to tease out.

The first is the most obvious reason, and, although highly problematic, seems less intriguing. The BD treatments themselves contribute to certain medical illnesses. The medications can be life-saving, but they take a heavy toll on the body. Lithium has been known to cause hypothyroidism. Lithium, Depakote, and a number of the atypical antipsychotics (Zyprexa is famous, or shall we say infamous, for this) cause weight gain, which can ultimately lead to obesity and thus cardiovascular issues, diabetes, and metabolic syndrome.

The problem exists, and must be dealt with.

But, despite what many people believe, there is high medical comorbidity among BD even when you factor out medication treatments.

The issues are complicated, and the underlying factors not always understood, but current research is hard at work developing theories as to why medical illness is so pervasive with BD.

Take an odd correlation, for example, that’s leading in a direction few could have foreseen.

The dread disease Multiple Sclerosis (MS) is the neurological disorder most consistently associated with BD. In fact, this comorbidity is twice the expected rate, with studies identifying BD in over 10% of MS patients (see Krishan 2005).

It has been known for years that MS is associated with lesions in the white matter of the brain. How fascinating it was to find, then, through MRI usage in the late 90s, that, according to PsychCentral’s review of the research,

“One of the most consistent findings to date has been the appearance of specific abnormalities, or lesions, in the white matter of the brain in patients with bipolar disorder.”

Thus researchers are currently hypothesizing that the comorbidity of BD and MS is related to the location of the lesions.

There’s an actual case where the problem is, indeed, all in one’s head.

Let’s move from the head to the neck.

The University of Maryland Medical Center published a piece about complications from bipolar disorder.

They note something irregular about thyroid conditions. It’s known that hypothyroidism, or low thyroid levels, is a common side effect of  lithium. However, it turns out that many BD patients (most frequently women) are at a high risk for hypothyroidism no matter what treatment they receive.

Willem Nolen, M.D., Ph.D., of the University of Groningen Medical Centre, Netherlands, found that bipolar patients were twice as likely as controls to develop autoimmune thyroiditis (AT). Both AT and hypothyroidism seem to pre-date the illness, and may even be risk factors.

In a hopeful note among all this bad news, research presented at the Sixth International Conference on Bipolar Disorder highlighted the correlation–and then suggested the possibility that a thyroid blood test could help identify those at risk for BD. So hold on to that thought; we may not have much to do with it this second, but hope springs eternal.

[For an explanation of how doctors use thyroid supplementation to manage treatment-resistant BD, check out the post "Beyond ‘Beyond Lithium’–Treament-Resistant Bipolar Maintenance, Or Not Staying Put, Part I."]

Then there’s the issue of obesity, which lies at the core of so many other health problems.

Dr. David J Printz, Director of the Bipolar Disorder Research Clinic, and his colleagues note in their 2011 paper that in one study 68% of bipolar subjects were either overweight (36%) or obese (32%).

Again, we’re separating this out from the gift of poundage so lovingly bestowed by the anticonvulsants and atypicals: bipolar people just tend to be heavier than the general population, with higher body mass index, a health risk in itself.

And in an utterly fascinating connection, body mass index (BMI) is correlated with the number of depressive episodes. Thus heavier people, some studies suggest, will cycle into the lower end of the mood pole more frequently than their thinner counterparts.

Turns out we can’t blame it all on medications. Several studies (see Elmslie 2000, as well, for another major one) indicate that the additional weight carried by so many BD people comes to them the way it comes to all flesh and blood.

Amy M. Kilbourne, internationally recognized scholar in the field of mental health, and colleagues published a study in the 2007 issue of Bipolar Disorders analyzing nutrition and exercise patterns among patients with BD.

The results were disappointing but do explain why so many people with the mood disorder are heavy. The authors wrote:

“Patients with BD were more likely to report poor exercise habits, including infrequent walking . . . or strength exercises . . . than those with no SMI [serious mental illness]. They were also more likely to self-report suboptimal eating behaviors, including having fewer than two daily meals and having difficulty obtaining or cooking food. Patients with BD were also more likely to report having gained ≥10 pounds in the past 6 months and were the least likely to report that their health care provider discussed their eating habits or physical activity.”

So goodbye size 6, hello diabetes [three times more common in those with BD than the regular population] and metabolic syndrome.

No discussion of medical comorbidity and BD is complete without addressing the issue of vascular disease, which wins the highly dubious distinction of being hands-down the biggest killer of those with this affective illness.

The graph below, from Weiner et al 2011, is the visual of the researchers’ analysis 2129 deaths of BD patients, highlighting the ‘top-four’ causes of death. 700 of the deaths (for those, like me, not terribly mathematically minded, that’s nearly one-third) were due to vascular disease (592 cardiovascular, 108 cerebrovascular).

Excess Deaths in Bipolar Disorder (see Weiner et al 2011)

The reason for such high rates of vascular death will come as no surprise by now. Poor diets and inadequate exercise. . .they’re invitations to a vascular event. Additionally, smoking is even more common among those with BD than those with other serious mental illnesses. A 2009 study found that people with BD are 7.3 times as likely to be current smokers as the general population. A distressingly high 66% of subjects were daily smokers.

Add to these the obesity, and the consequent hypertension [one Norwegian study (do they seem like a 'hyper tense group of people? I always thought not.) found BD patients had an "estimated . . .prevalence of hypertension of 61% . . .as compared with a prevalence of 41% in the general population"] and diabetes, and you’ve got a fertile ground for vascular mortality.

Remember how Kermit mournfully told us “it’s not easy being green”? Clearly the same goes for being bipolar. Between mood swings and medical comorbidities it’s a tough row to hoe.

But interventions can improve the situation to some extent. Focus on a regular, healthful diet. For goodness sake: finally quit smoking. Get up and move [see post on how exercise can actually reverse the brain shrinkage caused by the stresses of BD] . See your internist regularly for preventative care.

And try to keep the flame of hope alive, knowing that there’s research time and money being invested into how to treat co-occurring medical illnesses-and how to use the information to determine risk factors for BD.

The famous frog finally comes to terms with his color in his song, realizing:

“When green is all there is to be
It could make you wonder why,
but why wonder why?
Wonder, I am green and it’ll do fine.”

Well, BD is all there is to be if you’ve got it–no cures heading down the pike at breakneck speed–and it’s the same for the physical illnesses. Despite the pain and suffering, wondering why won’t get you very far.

Just hold on, take care of your disorder as best you can, treat your physical symptoms with preventative measures and proactive medicine, and–with luck and a prayer–”it’ll do fine.”

REFERENCES

Beyer J et al. Medical comorbidity in a bipolar outpatient clinical population. Neuropsychopharmacology 2005; 30(2):401-4.

Carney CP, Jones LE. Medical comorbidity in women and men with bipolar disorders: A population-based controlled study.Psychosomatic Medicine 2006; 68(5):684-691.

Kemp DE, et al. Medical and substance use comorbidity in bipolar disorder. Journal of Affective Disorders 2009; 116(1-2):64–69.

Kemp DE, et al. Medical comorbidity in bipolar disorder: relationship between illnesses of the endocrine/metabolic system and treatment outcome. Bipolar Disorder 2010; 12(4):404–413.

Krishman KRR. Psychiatric and medical comorbidities of bipolar disorder. Psychosomatic Medicine 2005; 67:1-8.

Kupfer D. The Increasing medical burden in bipolar disorder. JAMA 2005; 293(20):2528-2530.

McIntyre RS, et al. Medical comorbidity in bipolar disorder: Implications for functional outcomes and health service utilization. Psychiatric Services 2006; 57(8).

Printz D, et al. Weight gain in bipolar disorder: Causes and treatments. Primary Psychiatry 2003; 10(11):29-36.

Soreca I, Frank E, Kupfer DJ. The phenomenology of bipolar disorder: what drives the high rate of medical burden and determines long-term prognosis? Depression and Anxiety 2009; 26(1):73–82.

Weiner M, Warren L, Feiderowicz JG. Cardiovascular morbidity and mortality in bipolar disorder. Annals of Clinical Psychiatry 2011; 23(1):140-147.