Can medical illnesses cause symptoms of depression?

Definitely. In fact, before receiving any kind of treatment for depression, you should have a physical exam and blood work-up to rule out so-called medical mimics of depression. One study found that 10 percent of the problems patients came to outpatient mental health clinics for were probably due to medical illness. Another study conducted on a large number of patients in Canada who sought help from outpatient clinics found that roughly 34 percent of these patients had a medical illness that contributed to their psychiatric symptoms. Eighteen percent had an illness that was entirely responsible for the psychiatric problems.

Although there are hundreds of medical illnesses or conditions that can lead to symptoms of depression, only a handful are most common: alcohol or drug abuse, other prescription medications (especially those used to treat cardiovascular disease), glandular problems such as an under-active thyroid, neurological disorders such as multiple sclerosis, and sleep disorders.

Symptoms of depressionCan problems such as low blood sugar (hypoglycemia) cause depression?

The most common type of hypoglycemia – and the one people are usually referring to when they mention the connection between low blood sugar and mood – is acute reactive hypoglycemia.

When you eat, an organ in your body called the pancreas releases insulin to regulate metabolism of blood sugar. In some people, the pancreas secretes excessive insulin in response to eating a lot of sugary or starchy food quickly. Other people may have defective mechanisms for keeping their level of insulin in check once it is released by the pancreas. In either case, excessive insulin activity causes the blood sugar level to fall into the low-normal or below-normal range. The person may experience transitory symptoms such as anxiety, heart palpitations, restlessness, sweating, fatigue, and weakness. Some people may feel irritable and have other personality changes. These effects may last four to six hours, unless the person eats something.

This type of transient fluctuation in blood-sugar levels, even if repeated frequently, is unlikely to be a cause of depressive illness. In fact, severely depressed patients have generally been found to have a less than normal reduction in blood-sugar levels in response to insulin, not an exaggerated reduction. This may be because depressed people often have high levels of cortisol, which suppresses the action of insulin.

Chronic hypoglycemia, caused by an insulin-producing tumor, for instance, can mimic depression. Insulin-producing tumors and other causes of chronic hypoglycemia, however, are rare.

To be considered truly hypoglycemic, you must have (a) a glucose tolerance test (GTT) indicating your blood-sugar level is low and (b) signs and symptoms such as those indicated above, which coincide with the low blood-sugar level and which are relieved by the ingestion of sugar or other food. The reason is essential for the diagnosis is because 25 percent of individuals taking the GTT have below-normal blood-sugar levels without any symptoms at all. Up to 50 percent of women taking a GTT may have below-normal blood-sugar levels without symptoms.

Some doctors interpret the test much more liberally. They will diagnose hypoglycemia if the rate at which the blood-sugar level falls in the GTT is rapid. A number of alternative medicine practitioners swear by the antidepressant effects of an anti hypoglycemic diet.

What should the depressed person do?

First, you need to understand that the claims of the “hypoglycemic doctors” are just that: claims. There is no good evidence to suggest that hypoglycemia is a frequent cause of depression. In addition, there is no evidence to support the use of anti hypoglycemic diets as effective first-line treatment for depression. If you have symptoms suggestive of acute reactive hypoglycemia, you might want to get a GTT. Or, if you have the motivation, you can simply modify your diet by reducing the amount of carbohydrate you eat. This may be especially helpful if you crave sweets or starchy food.

Some depressed patients tend to overeat sweets or starchy foods (those with seasonal depressions and so-called atypical depression). This may contribute to an increased incidence of acute reactive hypoglycemia in some individuals.