Type 2 diabetes mellitus is one of the most common and costly chronic diseases, afflicting 16 million people nationwide. According to American Diabetes Association statistics, the disease each year costs the United States more than $100 billion in health-care expenses and lost productivity.
Diabetes is associated with many psychiatric conditions, yet psychiatrists may not be aware that patients under treatment for mental disorders are suffering from diabetes or have problems related to their psychopharmacologic therapy. With changing criteria for the diagnosis of diabetes, new evidence about the prevention and treatment of this disease, and a growing link between diabetes and psychiatric issues, the practicing psychiatrist should be knowledgeable about such possible interactions.
The following three cases illustrate these challenges and offer pearls for patient management.
PATHOPHYSIOLOGY OF DIABETES
Type 1 diabetes is caused by an autoimmune phenomenon leading to beta-cell failure and absolute deficiency in insulin. Type 2 diabetes is characterized by tissue receptor resistance to insulin (aggravated by genetic factors, obesity, aging, and other problems), beta cell dysfunction (with defects in the timing and amount of insulin secretion), and changes in hepatic glucose output and glucose transport. Patients with type 2 diabetes will initially lose phase one (early) insulin secretion in response to a glucose load.
Unregulated production of hepatic glucose ultimately leads to abnormal fasting blood sugars. The beta cells will initially compensate, but will eventually fail. Thus, postprandial blood sugars will increase, reflecting the loss of early insulin secretion, but return relatively rapidly to normal. Gradually, fasting blood sugars will also rise as insulin resistance becomes more pronounced and the imbalance in hepatic glucogenesis occurs. Eventually, with absolute beta cell failure, patients with type 2 diabetes will require insulin to offset their insulinopenic state.
Case 1: Diabetes and depression
L.S., age 54, has a five-year history of type 2 diabetes. On referral, he presents with increasing lethargy, difficulty concentrating, and irritability. His mental status examination discloses anhedonia, moderate irritability, depressed mood, loss of appetite, and overall lethargy. He emphatically denies suicidal thoughts, but feels “overwhelmed with life.” His referring physician notes that he also suffers from hyperlipidemia and hypertension, and continues to smoke one pack per day. His current medications include atorvastatin, enalapril, glucophage, and one baby aspirin per day. His weight is 247 pounds. Other than mild background retinopathy and mild peripheral neuropathy, his last physical examination was normal. His last HbA1c was 8.8%, and his creatinine was 1.7.
How do you manage this patient?
The challenge Type 2 diabetes mellitus affects more than one in 17 persons in the U.S., and physicians diagnose approximately 800,000 cases yearly. Yet one third of individuals with diabetes are undiagnosed, and multiple studies suggest we are falling short of accepted guidelines for care. Diabetes remains the leading cause of blindness, renal failure, and non-traumatic amputation in adults. While care for patients with diabetes will largely fall to primary care physicians (it is the third most common problem seen by family physicians) and endocrinologists, psychiatrists will often also see these patients.
Case 1 concluded While this patient’s history clearly suggests major depressive disorder, the possibility of other medical complications (e.g., worsening renal function or lactic acidosis from metformin therapy) should be entertained. A serum lactate level was normal and a metabolic panel, including renal function, was stable. The patient responded well to the addition of a selective serotonin reuptake inhibitor (SSRI) for his major depressive disorder.
Comment Many patients with diabetes will present with symptoms and signs suggestive of depression and anxiety. Patients with diabetes are more likely to develop depression, a disorder that worsens the outcomes for such individuals. These patients are likely to take multiple medications and have many medical comorbidities. Therapy of psychiatric disorders in patients with diabetes may be complicated by drug-drug and drug-disease interactions. When patients with diabetes present with symptoms of a mental disorder, a careful assessment is essential.
DIAGNOSING DIABETES
The diagnosis of diabetes depends on the demonstration of either fasting glucose intolerance (plasma glucose 126) or abnormal response to glucose challenge (plasma glucose 200 following a 75 gm glucose challenge). Testing is repeated and not done at a time of stress, such as during an acute illness. The HbA1c is not recommended for the diagnosis of diabetes.
Risk factors for type 2 diabetes mellitus include:
- Obesity
- Family history of diabetes
- Race/ethnicity (African-American, Hispanic, Asian-American, Pacific Islander)
- Age ≥ 45
- Sedentary lifestyle
- Previous history of impaired glucose tolerance
- History of gestational diabetes or birth weight of child of 4 kg or more
- Hypertension
- HDL 35 ≤ mg per dL or triglyceride 250 ≥ mg per dL