Which Mental Illness Is Most Disabling? - Psychology Today

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While there is no consensus on the exact definition of disability (especially psychological disability), there is greater recognition these days that, like physical disease, psychological conditions can cause functional impairment and dysfunction—some more so than others. In a paper, published in the November issue of Social Psychiatry and Psychiatric Epidemiology, Edlund et al. conclude that among the 15 mental health conditions examined, mood disorders (e.g., depression) are associated with the greatest functional impairment and disability.¹

The Mental Health Surveillance Study

Data for the present research came from the Mental Health Surveillance Study (MHSS). The MHSS is a sub-sample of 2008-2012 National Survey on Drug Use and Health (NSDUH), an annual survey of non-institutionalized US civilians 12 years or older. MHSS, however, includes only individuals aged 18 and over.

For the Mental Health Surveillance Study, researchers conducted phone interviews with participants, utilizing the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders-IV-TR. Of the original NSDUH 2008-2012 sample of 220,000 adults, 5,653 completed the MHSS interview (48% men; 67% White, 14% Latino/Hispanic, and 12% Black).

Using these interviews, researchers attempted to determine if participants met the criteria for any of the following 15 psychiatric conditions:

Mood disorders (major depressive disorder, mania, and dysthymic disorder), anxiety disorders (post-traumatic stress disorder, panic disorder, agoraphobia, social phobia, specific phobia, obsessive-compulsive disorder, and generalized anxiety disorder), alcohol use disorder, illicit drug use disorder, intermittent explosive disorder, adjustment disorder, and psychotic symptoms.

Other conditions (e.g., eating disorders) were not examined because of their low prevalence in the sample.

Three measures of disability

Functional impairment was assessed using three measures (modified for this investigation):

Scores for GAF range from 0 to 100 (higher means better functioning). GAF scores are based on both functional impairment and symptom severity (whichever happens to be worse).

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Unlike GAF, which is determined by clinical judgment and thus has a subjective element, WHODAS and DOR are based strictly on objective criteria and the patient’s responses.

DOR measures the number of days in the past year when an individual could not function at all because of mental health issues.

WHODAS assesses cognitive abilities (e.g., memory, concentration), social relations, social participation, self-care, and ability to do one’s duties (whether related to work, home, or school). In this study, a 0-24 score range was used, with the higher score meaning worse functioning.

Mental illness and disability: Results

Descriptive statistics revealed the sample’s average...

• GAF = 74.1 (median 75)
• WHODAS = 3.5 (median 1)
• DOR = 6.7 (median 0)

Researchers performed a series of regression analyses, and concluded that among 15 mental health conditions, mood disorders were associated with the greatest functional impairment; anxiety disorders, with intermediate functional impairment; and substance use disorders, with less functional impairment.

For instance, in the fully adjusted model, the greatest decrease in GAF scores was seen in psychotic symptoms (22), followed by depression (16), and mania (13). In WHODAS modeling, mania (9), depression (6), and social phobia (5) had the largest coefficients. And, in the final analysis, only depression, adjustment disorder, and panic disorder,  had a significant association with DOR.

These results are comparable with those of a 2007 study, which also included a nationally representative sample, used DOR, and employed similar statistical methods. In that investigation, mood disorders resulted in higher days-out-of-role than most other disorders examined.²

Commentary on use of disability measures

Aside from suggesting that mood disorders are associated with the greatest disability among conditions examined, the present investigation highlights the importance of using multiple measures in determining disability.¹

Employing a single measure paints a misleading picture. For instance, as mentioned above, the median value for days-out-of-role was zero. Indeed, 70% of participants with one mental disorder, and over half of those with two disorders, had zero days-out-of-role. Only 3/15 disorders were statistically linked with DOR scores (8/15 with WHODAS; all 15 with GAF).

Therefore, DOR was the least sensitive of the three measures used. If we were to rely only on days-out-of-role numbers, we would miss significant dysfunction and disability.

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While GAF is likely the most sensitive of the three measures, it does not always assess functional status. As mentioned, GAF scores depend on functional impairment and symptom severity; when there is disagreement between the two values, GAF score is determined by the worse of the two. For instance, if symptoms are severe but functioning is okay, GAF scores will still be low.

Thus, it is important to use complementary measures of disability; doing so allows clinicians to achieve greater accuracy in determining a patient’s needs and in monitoring a patient’s progress. Use of complementary measures can also inform public policy and resource allocation. Physicians, politicians, and the public cannot make informed decisions about how to improve functional impairment if they fail to recognize disability in the first place.

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