Depression Treatments Less Effective for Poor

January 6, 2006

Poverty was a marker for poor treatment-outcomes among people taking antidepressants, according to a recent study by Harvard researchers. The study analyzed data from an open-label phase of two trials in which participants took either nortriptyline or Paxil (paroxetine) and engaged in interpersonal psychotherapy.

The trials were funded by the National Institute of Mental Health (NIMH). The report by Alex Cohen, PhD, and colleagues, was published in the January issue of Archives of General Psychiatry and reported by MedPage Today on January 3, 2006.

The study showed that depressed people from poor neighborhoods were about half as likely to respond to treatment, compared with participants classified as middle income. Suicide ideation was also twice as common among low-income study participants, and they were 2.5-fold more likely to harbor suicidal thoughts, compared with high-income participants. Additionally, statistical analysis suggested an inverse relationship between income and suicidality.

The investigators found no associations between number of years of education and suicidal ideation or response rate, and no link was found between remission rates and economic status.

A possible explanation for the finding, the authors wrote, according to MedPage Today, is a prior observation that "the persistence of depressive episodes was more pronounced among individuals with lower [socio-economic status]. That is, if individuals with lower [socio-economic status] tend to have depressive episodes of greater duration, rates of difficult-to-treat depression may also be elevated in this population."

Clinical Trial

Both studies evaluated participants weekly for treatment-response and depressive symptoms. In both studies, participants' mean age was 72 years, and 75% of participants were women.

The study population in the first study consisted of 145 adults, including 25 living in poor neighborhoods, 92 in middle-class neighborhoods and 28 in high-income areas. The second study included 15 low-income participants, 66 middle-income participants and 22 high-income participants.

Researchers assessed education levels at the beginning of the original studies, using US Census Bureau information to assess median annual household income. Low-income was defined as <$25,000, middle-income was $25,000-$50,000 and high-income was >$50,000.

Dr Cohen et al noted that, although their findings were consistent with results of earlier studies, were several limitations existed: First, the authors pointed out that census tract data may provide an inaccurate reflection of participants' true income. Also, differences in treatment-response by socio-economic status lacked a placebo comparison.

Despite these limitation, the authors concluded that the results "suggest that social worlds, in interaction with demographic and clinical characteristics of individuals, may affect response to antidepressant treatment, even in clinical trials when subjects receive optimal pharmacologic and psychosocial treatments.

"Therefore, we suggest that future clinical trials routinely gather data on individual income, educational degrees earned, occupation, and aspects of the broader social environment such as social capital."

Sources:
Poverty Limits Efficacy of Treatment for Depression, MedPage Today, January 3, 2006.
Social Inequities in Response to Antidepressant Treatment in Older Adults. Cohen A et al, Archives of General Psychiatry, volume 63, pages 50-56, January 2006.

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