Investigators from the University of California–San Francisco have determined a surprisingly low prevalence of depression in people with type 1 diabetes when using a structured clinical interview compared with patient questionnaires. Their findings suggest that clinical depression may be overdiagnosed in people with type 1 diabetes and that depression according to self-report scales may in fact reflect the emotional distress associated with managing the condition.
The authors assessed 368 people with type 1 diabetes using the eight-item Patient Health Questionnaire Depression Scale (PHQ-8), the Type 1 Diabetes Distress Scale and a structured clinical interview to assess major depressive disorder (MDD). The PHQ-8 has a maximum score of 24, with higher scores indicating an increased likelihood of depression.
The prevalence of MDD according to PHQ-8 scores was 11.4%, 7.1% and 3.8% when cut-off scores of >10, >12 and >15, respectively, were used. Conversely, structured clinical interview according to Diagnostic and Statistical Manual-5 (DSM-5) specifications revealed a true MDD prevalence of 3.5%. This was similar to the rates found in the general US population in previous studies, which ranged from 4.1% to 7.0%. The prevalence of moderate or worse diabetes distress was 42.1%.
Depending on which PHQ-8 cut-offs were used, the rate of false-positive diagnoses ranged from 52% to 71%. Notably, a cut-off of >10, the most widely used cut-off for MDD on the PHQ-8, yielded the highest rate of false-positives. These findings reinforce the need to view the PHQ-8 and similar depression scales only as screening instruments for MDD, not substitutes for a formal diagnosis.
Notably, 92–96% of participants who were classified as having MDD on the PHQ-8 had moderate diabetes distress or worse, as did 92% of those with an official diagnosis of MDD.
These findings go against the commonly held view that there is an abnormally high rate of MDD among adults with type 1 diabetes, and they suggest that more specific therapy to treat diabetes distress may be more appropriate than treatment for affective disorders such as MDD. However, the authors caution that: “It should be noted, however, that 3.5% of the adults with 1 diabetes in our sample met the DSM-5 criteria for MDD on the [structured clinical interview]. In these cases, the severity of distress, regardless of cause, is sufficiently high to require intervention according to clinical guidelines.
The study can be read in full here.
