Causes of erectile dysfunction

There are two main groups of causes of erectile dysfunction: organic and psychogenic, and sometimes they occur in tandem.

Organic

Organic causes are causes that are a result of a physically identifiable cause such as a bodily disease, or a side effect of a drug.
The vast majority (85-90%) of erectile dysfunction is from an organic cause. The full list of causes is expansive. The most clinically relevant are: age, vascular disease, diabetes, lifestyle, neurological disease, prostate surgery/radiation, trauma and medications.

Age

Beginning at middle age, blood vessels within the penis become increasingly less pliable, making blood flow through the vessels more difficult.

Vascular disease

In men older than 50 years, nearly half of all erectile dysfunction is a result of vascular disease. Diseases include peripheral vascular disease, atherosclerosis, myocardial infarction and hypertension. Males who have had either a heart attack or open-heart surgery have a 60% chance of erectile dysfunction.

Diabetes

Diabetes is a common cause, with approximately one-half of all diabetic men experiencing erectile dysfunction at some point in their lives. Since diabetes has adverse effects on both blood vessels and nerves, the erectile dysfunction is likely a result of both. Maintaining optimal glucose control minimizes the risk of erectile dysfunction.

Lifestyle

Smoking is an independent risk factor for erectile dysfunction, accelerating atherosclerosis of penile blood vessels. Smokers are 50% more likely to get erectile dysfunction.
The MMAS study results show that men who do regular exercise are at lower risk of erectile dysfunction [Ref], likely due to positive cardiovascular effects.
Also, the MMAS study revealed that high-density lipoprotein (HDL)–the so-called “good cholesterol”–was associated with a reduced risk of erectile dysfunction.
The long-term intake of alcohol can damage conduction of nervous signals, resulting in a decreased ability to achieve satisfactory erections.

Neurological disease

Diseases of the nervous system are another cause, since intact nervous pathways are required for an erection. Disorders include stroke, Alzheimer disease, epilepsy and multiple sclerosis.

Prostate surgery/radiation

Prostate surgery can lead to erectile dysfunction, due to damage to nerves, blood vessels, or both. In surgery to reduce benign prostatic hyperplasia (BPH), the risk of erectile dysfunction is approximately 10-20%. In a radical prostatectomy, patients who are younger than 60 years have only a 20% chance of erectile dysfunction, but patients older than 70 years have a 90% chance. In radiation therapy for prostate cancer, 50% of men will experience erectile dysfunction within 5 years.

Trauma

Trauma to the vasculature or nervous pathways can lead to erectile dysfunction. Interestingly, bicycle riding is undergoing research as a possible factor causing such injury to the pelvic area, and bicycle seat manufacturers have been quick to respond with new bicycle seats designed to reduce pressure on this important area.

Medications

Both prescription and illicit medications can induce erectile dysfunction.
The commonest prescription medications which impair erections are: antihypertensives, antidepressants, antipsychotics, cholesterol-lowering agents, some anti-ulcer drugs, 5-alpha reductase inhibitors and hormonally active drugs such as finasteride.
Illicit medications include cocaine and ectasy (MDMA). Since MDMA can result in a temporary erectile dysfunction, some addicts use a concurrent Viagra tablet to counteract this effect [Ref]. This combination of MDMA and Viagra has been termed “sextasy”.

Psychogenic

Psychogenic refers to impotence from a psychological cause. Only 10-15% of all erectile dysfunction is due to psychogenic causes.
Psychogenic erectile dysfunction is characterized by good nocturnal and morning erections and negative lab investigations. Another hallmark finding is variable erections: normal one day and absent the next.
Depression is one of the best studied causes. The MMAS study found that depression was the second likeliest risk factor for erectile dysfunction (odds ratio of 1.82). Additionally, nearly 100% of men suffering from severe depression also have erectile dysfunction.
Other common psychogenic causes include anxiety (including performance anxiety), low self-esteem, stress and guilt. Even diseases such as post-traumatic stress disorder (PTSD) can be associated with erectile dysfunction.

Combination

Organic and psychogenic causes can often co-exist.
This can occur as a pure clustering of unrelated diseases, such as a diabetic patient with stress at work.
It can also occur as a clustering of risk factors. For example, the risks for vascular disease also increase the likelihood of depression. These risk factors include smoking, obesity and a sedentary lifestyle [Ref]. One study even coined the term “DEC syndrome”, referring to men suffering from depression, erectile dysfunction and coronary heart disease, since this triad of conditions is so common. Also, age increases the risk of both erectile dysfunction and the risk of depression.

Another interplay of organic and psychogenic causes is the medical treatment of a psychological disorder, such as depression. Depression is a cause of erectile dysfunction, and one of the most commonly used classes of anti-depressants are the selective serotonin reuptake inhibitors (SSRIs) which can also cause erectile dysfunction. Fortunately, one can usually readily treat the erectile dysfunction side effect of SSRIs with PDE5 inhibitors.

Psychological factors also can worsen impotence caused by a physical condition. Someone may experience anxiety about sex after a recent myocardial infarction, or low mood while adjusting to disability following a stroke.