These symptoms are also more specific when they develop in conjunction with at least 1 of the 2 cardinal symptoms of depression, so understanding the timing or onset of somatic symptoms is informative. Considering the etiology of the symptom, or whether the somatic symptom could be caused by diabetes can be helpful because symptoms unrelated to medical illness are more likely due to depression. And finally, if the somatic symptom is out of proportion to the illness, medication, or another relevant factor, it may be more likely due to depression.
Despite challenges associated with diagnosing depression in the medically ill, studies performed in ambulatory diabetic cohorts have been encouraging. In general, they have shown that common depression screening scales, including the BDI and Patient Health Questionnaire-9 (PHQ-9), retain both their sensitivity and specificity in identifying depression when administered in outpatient settings.15,16
Many studies have examined the effectiveness of treatment for depression in diabetic patients. This has included the examination of evidence-based psychotherapy; psychopharmacology; mixed-treatment modalities; and systems-based approaches, such as those using collaborative depression care models to treat depression in primary care (Table). Cognitive-behavioral therapy (CBT) with added emphasis on diabetes self-management can be effective at treating depression and may also help reduce HbA1c levels.
Psychopharmacological approaches have proved effective for treating acute depressive episodes, for maintenance therapy for MDD, and for successfully preventing relapse of depressive episodes. Moreover, there is observational evidence that antidepressant use may increase the risk of type 2 diabetes mellitus.17
Collaborative depression care programs have successfully improved depression outcomes. However, only multicondition collaborative care programs, such as TEAM-care, have demonstrated the ability to improve depression as well as diabetes-related measures such as blood pressure and HbA1c and low-density lipoprotein cholesterol levels.18
Choice of psychopharmacological agents in the treatment of depression in diabetic patients deserves special attention because depression in these patients is complicated not only by the adverse effects of medication but also by the effects of diabetes. For instance, some SSRIs may cause weight gain, which will exacerbate insulin resistance and may contribute to sexual dysfunction, worsening a common, long-term complication of diabetes. SSRIs may also cause drug-drug interactions via their effects on the cytochrome P-450 (CYP) isoenzymes by interfering with the metabolism of diabetes medications. For example, fluoxetine(Drug information on fluoxetine), fluvoxamine(Drug information on fluvoxamine), and sertraline may inhibit the CYP2C9 isoenzyme and affect the metabolism of the sulfonylureas tolbutamide(Drug information on tolbutamide) and glimepiride(Drug information on glimepiride).
TCAs, while effective for treating depression in diabetes, have unique properties that limit their usefulness. First, TCAs may cause elevations in fasting blood glucose levels and they are more likely to cause weight gain than other, newer antidepressants. Second, many adverse effects associated with TCAs, such as orthostasis and arrhythmia, are particularly problematic when diabetes itself targets the nervous and cardiovascular systems.
Bupropion, in particular, possesses many qualities attractive for treatment of the diabetic patient, and it has been found to be efficacious for depression in this population.19 This drug is weight-neutral (or may even help diabetic patients lose weight); it is associated with less sexual dysfunction; it can be effective for smoking cessation (a common and costly comorbidity in depressed diabetic patients); and it has shown efficacy in treating neuropathic pain.16,19 However, bupropion is ineffective for treating co-occurring anxiety disorders. Venlafaxine and duloxetine(Drug information on duloxetine), which have shown efficacy in treating depression and neuropathic pain, may also be useful in diabetic patients with depression.
Mr M, a 54-year-old with diabetes and hypertension, was referred for evaluation by his primary care physician. During the interview, Mr M rated his mood as “fair,” but he is experiencing decreased interest in leisurely activities, such as hiking and cigar smoking, as well as decreased motivation for self-care, including eating a healthy diet and taking regular blood sugar readings. He describes frequent nighttime waking, with no more than 3 hours of uninterrupted sleep; normal appetite, with a recent 5-lb weight gain; normal concentration; and decreased energy. He denies hopelessness but endorses feelings of guilt and describes himself as a bad partner to his wife because he’s currently unable to work and no longer engages in physical activity with her. When asked if he ever has thoughts of hurting himself or others, he replies, “Yeah, sometime I think I’m no good and people might be better off without me.”
Mr M is clearly depressed; he has decreased interest, guilty thoughts, feelings of being ineffective, and intermittent suicidal ideation. He’s not sleeping well (possibly because of polydipsia) and has decreased energy as well as a recent 5-lb weight gain. Additional history about the duration of both his depression and diabetes may be helpful, as would specific symptoms that the patient attributes to his diabetes, including the severity of these symptoms. Knowing the time of onset of his decreased interest and somatic symptoms may be useful. Direct inquiry into whether the patient suffers from anxiety, sexual dysfunction, or neuropathy may also help guide treatment.
We recommend administering the PHQ-9 and Montreal Cognitive Assessment during the initial patient evaluation. These examinations should be repeated regularly over time to track the patient’s progress and response to treatment. Additional history can be obtained from the patient’s primary care physician. Pending further history, CBT with an emphasis on diabetes self-care should be discussed as a possible option, as should treatment with bupropion, an SSRI, or a dual-acting agent.