Results. The etiology of impotence in men with diabetes has been the source of much debate. Early studies divided all causes of impotence into two groups – organic impotence, with lack of nocturnal penile tumescence, and psychogenic impotence, with intact nocturnal penile tumescence. Early studies stopped with an "organic" finding, neglecting psychological effects of impotence. Men with diabetes were classified as having an organic impotence pattern greater than 90% of the time versus the 90% psychogenic pattern found in the general population. Recent studies have found it difficult to distinguish between psychogenic and organic causes of impotence. Nocturnal penile tumescence results which originally were the gold standard for classifying impotence as organic have been found to be influenced by depression, and can return to normal after the resolution of a depression. A more appropriate model is one that recognized the contributions of physiologic, affective, and cognitive factors to erectile function. The correlation between impotence and neuropathy appears to be especially strong. There is also a suggestion of a role for vasculopathy. One study found that most men with diabetes and impotence have neurogenic abnormalities. Since many men without impotence did as well, a second factor was required. Either depression or vasculopathy combined with neuropathy resulted in impotence. Depression is both common and frequently unrecognized in patients with diabetes. Depressive symptoms are more common in men with sexual dysfunction. Depression in patients with impotence may be both contribution to and a consequence of impotence, which can lead to not only depression but self-depreciation, demoralization, and performance anxiety.

Conclusion. In considering impotence in patients with diabetes, not only do neurologic, vascular, endocrine, and pharmacological causes need to be considered but so do psychogenic causes. Even in patients where psychological factors may not be the initial cause of impotence, these factors often then become part of the sexual dysfunction and if not addressed, medical treatments are more likely to fail.