Still, the mind plays an important role. Every sexual act begins with mental impulses of erotic arousal, and emotional problems account for 20% of all erectile dysfunction severe enough to qualify as impotence. Psychological factors are also responsible for the temporary sexual dysfunction that affects nearly every man at some time in his life.

So the mind can certainly influence erectile function, but is the reverse also true? Can erectile dysfunction affect the mind? A Columbia University study says the answer is yes. The subjects were 152 men with an average age of 56. They all had mild to moderate depression that was documented by an objective test, the Hamilton Depression Rating Scale. None of the men were taking antidepressant medications during the trial, which lasted 12 weeks. All the volunteers had erectile dysfunction that had lasted for at least six months; the average duration was six years. The men were evaluated at 20 urology clinics around the country, and all were found to have normal hormone levels. Each man had a stable relationship with a female partner, and none was taking nitroglycerin or other nitrate medications.

The men were randomly assigned to two groups; 74 men received sildenafil (Viagra), to be taken one hour before sexual intercourse; 78 received placebos. As expected, sildenafil was much more effective than the placebo in restoring sexual function. But the study also found that men who experienced good erectile function also enjoyed an improvement in their depressive symptoms and overall quality of life. In fact, 76% of the men who were successfully treated for erectile dysfunction enjoyed an improvement in their mild to moderate depressive symptoms, but only 14% of the men who did not respond to treatment experienced a similar benefit. Sildenafil also produced more side effects than the placebo (47% vs. 13%), but they were generally brief and mild (flushing, headaches, indigestion, and visual disturbances).

Like its newer rivals tadalafil and vardenafil, sildenafil is highly effective for erectile dysfunction, but it is not an antidepressant. The new research will not turn Viagra into Prozac, but it does remind us that the mind and body are inseparable parts of a single organism. Mental distress can certainly produce physical dysfunction, and sexuality is a prime example. But physical problems can also affect mood and mental outlook, and sexual dysfunction is an example of that, too.

In the last analysis, it's not a horse and cart question. Instead, physical health and mental health go together like hand in glove.