Erectile Dysfunction Causes: What the Evidence Shows, From Blood Vessels to Medicines

Erectile dysfunction is rarely caused by one thing. An erection needs healthy blood vessels, working nerves, enough testosterone, the right chemical signals and a mind that is not getting in the way. A problem at any of those points can cause ED, and most men with it have more than one.

This guide goes through each cause with the evidence behind it: the large population studies that measured how common ED is and who gets it, the 2018 American Urological Association (AUA) guideline, the cohort studies that link ED to later heart disease, and the drug labels that report how often common medicines cause it.

The short answer

The most common physical cause of ED is reduced blood flow, driven by the same things that damage arteries elsewhere: age, high blood pressure, diabetes, high cholesterol, smoking, obesity and inactivity. Nerve damage, low testosterone, some medicines and psychological factors such as anxiety and depression are the other main causes. Because ED shares its causes with heart disease, it can be an early warning sign, and the AUA advises that every man with ED is told this. Several causes can be improved or reversed, which is why finding the cause matters as much as treating the symptom.

How an erection works, and where it can fail

Sexual stimulation makes nerves in the penis release nitric oxide. Nitric oxide raises a messenger called cyclic GMP, which relaxes the smooth muscle in the penile arteries and erectile tissue. Blood flows in, the tissue expands, and the expansion squeezes the veins that would otherwise drain it. An enzyme called PDE5 then breaks cyclic GMP down, which helps the erection subside.

Each step points to a group of causes:

• Signal: desire, arousal and the brain's messages (psychological causes, low testosterone).
• Nerves: the message reaching the penis (diabetes, spinal cord injury, pelvic surgery).
• Blood vessels: arteries able to widen and fill the penis (vascular disease).
• Tissue: erectile tissue able to expand and trap blood (Peyronie's disease, injury, ageing tissue).
• Chemistry: anything that interferes with the process, including many medicines.

The main causes at a glance

Type of cause	Examples	Typical pattern
Vascular	Hardened or narrowed arteries, high blood pressure, high cholesterol, smoking	Gradual onset, worse over months or years, morning erections weaker
Metabolic	Diabetes, obesity	Gradual, often with other signs of diabetes
Neurological	Diabetic nerve damage, spinal cord injury, multiple sclerosis, prostate or bowel surgery	Linked to the injury, surgery or disease
Hormonal	Low testosterone	Often with low desire and tiredness
Medicines	Some prostate drugs, thiazide diuretics, antidepressants and others	Starts after a new medicine or dose change
Psychological	Performance anxiety, depression, stress, relationship conflict	Sudden onset, depends on the situation, erections at other times preserved
Structural	Peyronie's disease, penile injury	Curvature, pain or a lump in the penis

These overlap. A man with diabetes can have vascular and nerve damage together, and anxiety about sex often follows a physical problem and makes it worse.

Age: the strongest single factor

The Massachusetts Male Aging Study surveyed a random sample of men aged 40 to 70 in the late 1980s. 52% reported some degree of ED, from minimal to complete. Complete ED tripled from 5% at age 40 to 15% at age 70, and age was the variable most strongly linked to ED.

The same men were followed for an average of 8.8 years. Among 847 who had no ED at the start, new cases appeared at 25.9 per 1,000 men per year, rising sharply with each decade.

Age at start of study	New cases of ED per 1,000 men per year (95% CI)
40 to 49	12.4 (9.0 to 16.9)
50 to 59	29.8 (24.0 to 37.0)
60 to 69	46.4 (36.9 to 58.4)

A national US survey from 2001 to 2002 put ED at 18.4% of all men aged 20 and over. Part of the age effect reflects the slow build-up of the other causes below. Those causes stayed linked to ED after allowing for age in both studies, but age remained the strongest single factor.

Blood vessels: the most common physical cause

The AUA guideline states that the most common underlying mechanism of ED is vascular, and that ED and cardiovascular disease share causes and biology. Penile arteries are narrow, so the same damage that slowly narrows the arteries of the heart can show up in the penis first.

The guideline gives the scale of the overlap:

• High blood pressure is present in 38% to 42% of men with ED, and about 35% of men with high blood pressure have some degree of ED.
• Up to 42.4% of men with ED also have high cholesterol.
• Men with poor or very poor erectile function had twice the odds of a raised total to HDL cholesterol ratio.

Treated high blood pressure adds a complication, because some blood pressure medicines can also contribute to ED. That is covered in the medicines section below. It is rarely a reason to stop treatment, since uncontrolled blood pressure damages erections too.

ED as an early warning of heart disease

Because the causes are shared, ED often appears before heart problems do. The AUA guideline says symptoms of ED may come up to five years before a cardiovascular event, and that every man with ED should be counselled that it is a risk marker for cardiovascular disease.

The strongest evidence is a 2013 meta-analysis of 14 cohort studies covering 92,757 men followed for an average of 6.1 years.

Outcome in men with ED against men without	Relative risk (95% CI)
Heart attack	1.62 (1.34 to 1.96)
Any cardiovascular event	1.44 (1.27 to 1.63)
Stroke and other cerebrovascular events	1.39 (1.23 to 1.57)
Death from any cause	1.25 (1.12 to 1.39)
Cardiovascular death	1.19 (0.97 to 1.46), not statistically significant

The link was stronger in younger men, and stronger when ED was measured with a questionnaire rather than a single question. In the placebo group of a large US prostate cancer prevention trial, men with ED had a hazard ratio of 1.45 for later cardiovascular events after adjusting for other risk factors, which the authors described as similar to the risk from current smoking or a family history of heart attack.

This is an association, not proof that ED causes heart disease. The practical point is that ED is a reason to have your blood pressure, cholesterol and blood sugar checked. Our guide to ED in young men covers why this matters most when ED starts early.

Diabetes

ED is one of the most common complications of diabetes. High blood sugar damages both the small blood vessels and the nerves that erections depend on, so men with diabetes often have two causes at once.

• In the national US survey, 51.3% of men with diabetes reported ED, and diabetes was independently linked to ED after accounting for other factors.
• Depending on the severity and duration of diabetes, the AUA gives a range of 20% to 85%.

ED can be the symptom that leads to a diabetes diagnosis, which is why the AUA suggests checking fasting glucose or HbA1c. ED tablets work in diabetes, though less well than in men without it. Our diabetes and ED guide covers this in more detail.

Nerve damage

The nerves that trigger an erection run deep in the pelvis. Anything that damages them can cause ED even when the blood supply is healthy:

• Diabetic nerve damage (neuropathy).
• Spinal cord injury and multiple sclerosis.
• Surgery in the pelvis, most often radical prostatectomy for prostate cancer, and major bowel or bladder surgery.
• Pelvic radiotherapy.

Nerve-related ED responds less predictably to tablets. After prostate surgery in particular, success rates on sildenafil are lower than in other groups. Our sildenafil guide has the figures by cause.

Low testosterone

Testosterone drives sexual desire and supports erectile function. The AUA guideline recommends measuring morning total testosterone in every man with ED. Testosterone deficiency is defined as a total testosterone below 300 ng/dL together with symptoms and signs, confirmed on at least two morning samples.

Morning timing matters because levels fall through the day. The guideline notes that late afternoon values can be about 20% lower than morning values in young men. Acute illness, chronic illness and medicines such as opioids can also lower the reading.

Low testosterone tends to cause low desire and weaker morning erections as well as ED. Treating a real deficiency can help, and the AUA says men with deficiency should be told that ED tablets may work better when combined with testosterone therapy. Testosterone is not a treatment for ED in men whose levels are normal.

Medicines that can cause ED

Many medicines list ED as a side effect. The evidence ranges from well measured to anecdotal. These are examples where the drug's own label or a randomised trial gives numbers.

Medicine	Evidence	ED or impotence on drug	On placebo
Finasteride 5 mg (prostate enlargement)	FDA label, 4 year trial	8.1% in year 1; 5.1% in years 2 to 4	3.7% in year 1; 5.1% in years 2 to 4
Dutasteride 0.5 mg (prostate enlargement)	FDA label, pooled 2 year trials	4.7% in months 0 to 6; 0.8% in months 19 to 24	1.7%; 0.9%
Chlorthalidone (thiazide-type diuretic)	Randomised trial, TOMHS (557 men across six treatment groups, all with lifestyle counselling)	17.1% new erection problems by 24 months; no significant difference by 48 months	8.1% by 24 months
Paroxetine (SSRI antidepressant)	FDA label, 8 to 12 week trials	2% to 9% impotence across the conditions studied (plus much more common ejaculation problems)	0% to 3%

Two patterns stand out. With the prostate drugs, the excess in new ED reports came in the first year and then matched placebo. Both labels also describe sexual side effects that continued after stopping, and say the drug's role in that is unknown or cannot be established. In the blood pressure trial, the other drugs tested (acebutolol, amlodipine, doxazosin and enalapril) had ED rates similar to placebo, and many men with ED on treatment did not need to stop their medicine.

The paroxetine label warns that SSRIs as a class can cause erectile dysfunction, decreased libido and delayed or absent ejaculation. Other medicines commonly linked to ED include some beta blockers, antipsychotics, opioids and hormonal treatments for prostate cancer. Never stop a prescribed medicine on your own because of ED. A doctor can often switch to a drug with less effect on sexual function. Our finasteride side effects guide covers that drug in detail.

Psychological causes

The AUA guideline lists depression, anxiety, stress and relationship conflict as factors that can cause ED directly or add to a physical cause. Men often do not realise that these can interfere with the physical process of an erection.

• Performance anxiety: worry about failing triggers the stress response, which works against the relaxation of penile blood vessels. One bad experience can start a cycle.
• Depression: lowers desire and arousal. In AUA-cited surveys of men with ED, 11% reported depression. Some antidepressants add their own sexual side effects.
• Stress and relationship problems: reduce desire and make arousal harder.

Psychological causes are more likely when ED starts suddenly, happens with one partner or situation but not others, or when erections during sleep, on waking or during masturbation are normal. The AUA recommends considering referral to a mental health professional as part of treatment, whatever the cause, because anxiety and relationship strain so often come along with ED.

Smoking

Smoking damages the lining of blood vessels and is a recognised independent risk factor for ED. A 2014 meta-analysis of 10 observational studies with 50,360 men found a dose-response relationship. Nine of the ten studies were cross-sectional, so this shows association rather than proof of cause:

• Each additional 10 cigarettes a day was associated with 14% higher odds of ED (odds ratio 1.14, 95% CI 1.09 to 1.18).
• Each additional 10 years of smoking was associated with 15% higher odds (odds ratio 1.15, 95% CI 1.10 to 1.19).

In the Massachusetts study, smoking was linked to a higher chance of complete ED in men who also had heart disease or high blood pressure. Stopping removes an ongoing source of damage, though how much function returns depends on how much damage has already been done.

Weight, activity and diet

Obesity and inactivity are independent risk factors in their own right, and they drive diabetes, high blood pressure and high cholesterol. The national US survey found lack of physical activity independently linked to ED.

The clearest evidence that fixing them helps comes from a randomised trial in Italy. 110 obese men aged 35 to 55 with ED, but without diabetes, high blood pressure or high cholesterol, were given either a detailed programme to lose 10% or more of their body weight and exercise more, or general advice. After two years:

Measure	Diet and exercise programme (n=55)	General advice (n=55)
Body mass index	36.9 to 31.2	36.4 to 35.7
Physical activity, minutes per week	48 to 195	51 to 84
Erectile function score (IIEF-5)	13.9 to 17	13.5 to 13.6
Normal erectile function (score 22 or more)	17 men (31%)	3 men (5.5%)

About a third of men in the programme reached normal erectile function, against 5.5% with general advice, so the programme added about 25 percentage points. The AUA recommends that men with ED and related conditions be counselled that diet and exercise improve overall health and may improve erectile function.

Structural problems in the penis

Less commonly, the problem is in the erectile tissue itself. Peyronie's disease causes scar tissue that can bend the penis, cause pain and weaken erections. It was more common in older than younger men in a study of new ED patients. Injury to the penis or pelvis can damage tissue, arteries or nerves. The AUA guideline asks doctors to ask about changes in the shape of the penis for this reason.

For young men whose ED comes from a focal blockage in a pelvic or penile artery, often after injury, and who have no wider vascular disease and no venous leak, the AUA says penile artery reconstruction may be considered. It does not recommend surgery on the penile veins.

Conditions that often come with ED

The AUA guideline highlights several conditions that commonly appear alongside ED and need their own assessment:

• Premature ejaculation: reported by about 30% to 60% of men with ED in surveys. Some men with ED rush to finish before the erection fades, and some with premature ejaculation develop anxiety that causes ED.
• Urinary symptoms from an enlarged prostate: strongly associated with ED. Some prostate treatments can also affect erections or ejaculation.
• Depression: both a cause and a consequence.

Physical or psychological: telling them apart

The AUA describes vascular disease as the most common underlying mechanism, and psychological factors often sit on top of a physical cause. Some clues help separate the two, though none is conclusive:

More likely physical	More likely psychological
Gradual onset over months or years	Sudden onset, often after a stressful event
Happens in every situation	Happens with a partner but not alone, or only in some situations
Weaker or absent morning erections	Normal erections on waking or with masturbation
Risk factors such as diabetes, smoking or heart disease	Anxiety, low mood or relationship difficulty

Overnight erection testing was once used to make this distinction. The AUA guideline notes it is prone to false negatives and less useful in men with disturbed sleep.

What a doctor will check

The AUA guideline sets out the core assessment:

1. History: medical, sexual and psychosocial, including medicines, onset, and changes in desire, orgasm or penile shape.
2. Examination: blood pressure, pulse, genital examination, and signs of hormone or nerve problems.
3. Questionnaire: a validated score such as the five-item SHIM (IIEF-5) to measure severity and track treatment.
4. Blood tests: morning testosterone for every man; fasting glucose or HbA1c, fasting lipids and kidney function where recent results are not available; thyroid tests or PSA in some men.
5. Cardiovascular risk: counselling that ED is a risk marker, and referral where needed.

SHIM (IIEF-5) score	Meaning
22 to 25	No ED
17 to 21	Mild
12 to 16	Mild to moderate
8 to 11	Moderate
5 to 7	Severe

Which causes can be reversed

• Lifestyle factors: in the trial above, about a third of obese men in a weight loss and exercise programme reached normal function, against 5.5% with general advice. Stopping smoking removes ongoing damage.
• Medicines: ED from a medicine often improves after a switch, which a doctor can arrange.
• Low testosterone: treating a confirmed deficiency can improve desire and erections, and help tablets work.
• Psychological causes: often respond well to therapy, sometimes combined with a short course of tablets to break the anxiety cycle.
• Established vascular or nerve damage: usually not reversible, but very treatable.

Treatment works across most causes

The AUA says every man with ED should be told about PDE5 inhibitor tablets unless they are unsuitable for him. Sildenafil, tadalafil, vardenafil and avanafil work across vascular, diabetic, nerve-related and psychological ED, though less well after prostate surgery and in long-standing diabetes. Our comparisons of tadalafil and sildenafil and the generic Cialis guide explain the differences, and how to take sildenafil safely covers who should not take them.

Tablets treat the symptom, not the cause. A man whose ED comes from undiagnosed diabetes or early vascular disease still needs that found and treated.

When to see a doctor

See a doctor if ED lasts more than a few weeks, keeps coming back, or worries you. See one sooner if it started after a new medicine, comes with pain or curvature, comes with low desire and tiredness, or if you have chest pain, breathlessness on exertion, or known diabetes, high blood pressure or high cholesterol. Our erectile dysfunction page covers the full range of treatment.

Sources

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• Johannes CB et al. Incidence of erectile dysfunction in men 40 to 69 years old: longitudinal results from the Massachusetts Male Aging Study. J Urol 2000;163(2):460-3. PMID 10647654.
• Selvin E et al. Prevalence and risk factors for erectile dysfunction in the US. Am J Med 2007;120(2):151-7. PMID 17275456.
• Vlachopoulos CV et al. Prediction of cardiovascular events and all-cause mortality with erectile dysfunction: a systematic review and meta-analysis of cohort studies. Circ Cardiovasc Qual Outcomes 2013;6(1):99-109. PMID 23300267.
• Thompson IM et al. Erectile dysfunction and subsequent cardiovascular disease. JAMA 2005;294(23):2996-3002. PMID 16414947.
• Esposito K et al. Effect of lifestyle changes on erectile dysfunction in obese men: a randomized controlled trial. JAMA 2004;291(24):2978-84. PMID 15213209.
• Cao S et al. Association of quantity and duration of smoking with erectile dysfunction: a dose-response meta-analysis. J Sex Med 2014;11(10):2376-84. PMID 25052869.
• Grimm RH et al. Long-term effects on sexual function of five antihypertensive drugs and nutritional hygienic treatment in hypertensive men and women (TOMHS). Hypertension 1997;29(1 Pt 1):8-14. PMID 9039073.
• Capogrosso P et al. One patient out of four with newly diagnosed erectile dysfunction is a young man. J Sex Med 2013;10(7):1833-41. PMID 23651423.
• PROSCAR (finasteride) and AVODART (dutasteride) US prescribing information, section 6.1. PAXIL (paroxetine) US prescribing information, sections 5.13 and 6.1. DailyMed.

This article is for information only and is not medical advice. ED can have serious underlying causes. Talk to a doctor about new or persistent erection problems.