There's a danger that depression is being overdiagnosed by busy family doctors, who are not trained in psychiatric problems and instead rely on the PHQ-9 questionnaire, which was developed by Pfizer, the drug company that makes the top-selling antidepressants Zoloft (sertraline) and Effexor (venlafaxine).
Although an antidepressant prescription can be determined by responses to the PHQ-9, a major study has found that it is inadequate, and shouldn't be relied on for a clinical diagnosis. Researchers from the University of Leicester looked at 40 previously-published studies, involving 14,760 adults, 14 per cent of whom had major depression. The test can't accurately identify cases of depression, but can only rule out patients who aren't depressed, the researchers concluded.
The PHQ-9—or Patient Health Questionnaire—asks nine questions that have four possible answers, from 'not at all' to 'nearly every day'. The patient is asked whether he or she has little interest or pleasure in doing things, feels down or depressed, has trouble sleeping, feels tired, has poor appetite, feels bad about themselves, has trouble concentrating, moves or speaks slowly, and has thoughts of self-harm or wanting to be dead.
The answers notch up scores that range from 0 to 27, and an antidepressant prescription can be triggered by the doctor's judgement and any score that is above 10.