Erectile dysfunction is usually physical, not psychological — and most often it's about blood flow. An erection is a vascular event: arteries widen, blood fills the penis, veins close off to keep it there. Anything that interferes with blood vessels, nerves, hormones or the medicines you take can interfere with erections. Around one in five UK men experience ED, including many under 40, and in most cases there's an identifiable, treatable cause.
How an erection actually works
Arousal triggers nerves to release nitric oxide in the penis, which relaxes blood-vessel walls and lets blood flow in at up to several times the normal rate. The filling tissue compresses the veins that would drain blood out, trapping it — that's rigidity. The chain has several links: brain, nerves, hormones, arteries, veins. ED means one or more links is underperforming, and identifying which one is the useful question.
The physical causes
Blood-flow (vascular) problems — the most common
The arteries supplying the penis are narrow — around 1–2 mm, versus 3–4 mm for the heart's coronary arteries. That's why the same processes behind heart disease (atherosclerosis, high blood pressure, high cholesterol, smoking, diabetes) often show up in the penis first. Persistent ED, especially in your 40s or 50s, is recognised as an early warning sign of cardiovascular disease and worth a health check in its own right — we cover this fully in ED and cardiovascular health.
Diabetes
Raised blood sugar damages both the small blood vessels and the nerves involved in erections, which is why ED is significantly more common — and tends to appear earlier — in men with diabetes.
Hormones
Low testosterone can reduce desire and contribute to erection difficulties, though it's a less common primary cause than people assume — see testosterone and ED. Thyroid problems and raised prolactin can also play a role.
Medicines and substances
Some blood-pressure medicines, antidepressants (particularly SSRIs), and other prescriptions can affect erections — never stop a medicine yourself, but do mention the timing to a clinician, because alternatives often exist. Alcohol (short-term and long-term), smoking (a major vascular culprit), and recreational drugs all contribute.
Neurological and structural causes
Nerve damage from surgery (notably prostate surgery), spinal injury, multiple sclerosis or long-distance cycling pressure, and structural conditions such as Peyronie's disease, account for a smaller share.
The psychological side — real, but often secondary
Stress, anxiety, depression, relationship difficulties and performance anxiety all genuinely cause or worsen ED — the brain starts every erection. A useful clue: if you get firm morning or spontaneous erections but struggle during sex, the machinery works and the cause is more likely psychological. If erections are absent or weak in all situations, think physical first. Very commonly it's both: a physical cause creates a bad experience, anxiety about repeating it then compounds the problem. Treating the physical side often breaks that loop.
Age isn't a cause by itself
ED gets more common with age because the conditions that cause it accumulate — not because erections have an expiry date. Plenty of men in their 70s and 80s have no ED; plenty in their 20s and 30s do, where the causes skew toward anxiety, alcohol, recreational drugs and, increasingly recognised, porn-related conditioning. At any age, "just getting older" is a reason to investigate, not to accept.
Why the cause matters — and why treatment works anyway
Identifying the cause matters because some of them (cardiovascular risk, diabetes, low testosterone, depression) deserve treatment in their own right. But here's the encouraging part: PDE5 inhibitor treatments such as sildenafil and tadalafil work across most causes, because they amplify the blood-flow signal regardless of what weakened it. Effective treatment plus addressing the underlying cause — better cardiovascular health, drinking less, managing stress — is the combination that fixes both the symptom and the source.
Frequently asked questions
Is ED usually physical or psychological?
Physical causes — mostly blood-flow related — are the majority, especially over 40. Under 40, psychological factors are more prominent. Morning erections that work fine point toward psychological; absent erections in all situations point physical.
Can ED be an early sign of heart disease?
Yes — the penis's small arteries show atherosclerosis before the heart's larger ones. New, persistent ED in mid-life is a recognised prompt for a cardiovascular check.
Does watching porn cause ED?
Heavy use can condition arousal patterns that make partnered sex harder for some men — reported particularly in younger age groups. It's one contributor among several, and typically reversible.
Should I see a doctor or just get treatment?
Both have value. Online treatment is legitimate and effective, and any good consultation screens for red flags — but new ED alongside chest pain, breathlessness or diabetes symptoms deserves a GP review too.
References
- British Association of Urological Surgeons. Erectile dysfunction (impotence). baus.org.uk.
- NHS. Erection problems (erectile dysfunction). nhs.uk.
- Montorsi P, et al. Association between erectile dysfunction and coronary artery disease: the COBRA trial. Eur Heart J. 2006.
- Yafi FA, et al. Erectile dysfunction. Nat Rev Dis Primers. 2016;2:16003.