Erectile dysfunction is not a single condition with a single cause. It is a symptom — one that can arise from vascular disease, hormonal imbalance, psychological factors, neurological damage, medication side effects, or a combination of several of these simultaneously. The treatment that works depends entirely on which cause — or causes — are present.
This matters because the most common clinical mistake in managing ED is treating the symptom without identifying the cause. A man prescribed medication without any investigation of why he has ED is being offered symptom management for a condition whose cause has never been established. In some cases, the cause is entirely reversible. In others, a specific treatment — focal shockwave therapy, hormonal management, or psychosexual assessment — would address the underlying problem directly rather than working around it.
Understanding why ED happens is the most important step toward addressing it properly. This guide covers every recognised cause of erectile dysfunction, how common each is, how to identify which applies to you, and what the appropriate clinical response looks like. For an overview of the full treatment pathway, see our Erectile Dysfunction Treatment London service page, or our complete guide to erectile dysfunction in London for every treatment option compared.
"The most common clinical mistake in managing ED is treating the symptom without identifying the cause."
How Erections Work — and Where Things Go Wrong
To understand the causes of ED, it helps to understand the normal mechanism of erection. Sexual arousal triggers the release of nitric oxide in the penile tissue. Nitric oxide causes the smooth muscle of the penile arteries to relax, allowing blood to flow into the corpus cavernosum — the erectile tissue — under pressure. As the corpus cavernosum fills, the veins that would normally drain blood are compressed, trapping the blood and sustaining the erection.
This process requires:
- Adequate arterial blood supply to the penis
- Healthy endothelium (the inner lining of blood vessels) capable of producing nitric oxide
- Intact nerve pathways from brain to penis
- Appropriate hormonal signalling (testosterone)
- Psychological readiness — absence of inhibitory signals from anxiety or depression
Dysfunction at any of these points produces erectile dysfunction. Most men with ED have dysfunction at more than one point — which is why a comprehensive assessment matters.
The Main Causes of Erectile Dysfunction
1. Vascular Disease — The Most Common Cause
Vascular causes account for the majority of ED in men over 40. The mechanism is endothelial dysfunction — damage or impairment of the inner lining of the penile blood vessels, reducing their ability to produce nitric oxide and dilate adequately in response to sexual arousal. If you are over 50, see our dedicated guide to erectile dysfunction after 50 for what's normal with ageing and what isn't.
The same process drives cardiovascular disease — atherosclerosis, arterial stiffening, and reduced blood flow. This is why erectile dysfunction is now recognised as an early marker of cardiovascular disease. A meta-analysis published in Circulation found that men with ED have a 44% increased risk of cardiovascular events — and that ED typically precedes cardiac symptoms by three to five years. (Vlachopoulos C et al., Circulation, 2010)
Conditions associated with vascular ED:
- Cardiovascular disease and atherosclerosis
- Type 2 diabetes — damages both blood vessels and nerves
- Hypertension — accelerates endothelial dysfunction
- High cholesterol (dyslipidaemia) — promotes arterial plaque formation
- Obesity — associated with endothelial dysfunction and low testosterone
- Smoking — directly toxic to vascular endothelium
- Peripheral vascular disease
How it presents: ED that is consistent rather than situational, progressive over time, worse with cardiovascular risk factors, often associated with reduced morning erections.
What helps: Focal shockwave therapy — the only currently available non-invasive treatment that addresses vascular ED at the tissue level by stimulating angiogenesis and endothelial repair. Cardiovascular risk factor modification — blood pressure control, smoking cessation, weight loss — slows progression and in some cases produces meaningful improvement. (Esposito K et al., JAMA, 2004)
2. Psychological Causes
Psychological factors are the most common cause of ED in younger men and a significant contributing factor in men of all ages. They include:
- Performance anxiety — the most common psychological cause. A single difficult experience leads to anticipatory anxiety before the next sexual encounter. Anxiety activates the sympathetic nervous system — releasing adrenaline, restricting blood flow — which directly inhibits the erectile mechanism. The feared outcome becomes more likely, reinforcing the anxiety in a self-perpetuating cycle.
- Depression — reduces libido, impairs motivation, and directly affects the neurochemical pathways involved in sexual arousal. Many antidepressant medications also cause ED independently of the depression itself.
- Relationship difficulties — unresolved conflict, poor communication, loss of attraction, or trust issues can suppress sexual desire and function in ways that are not consciously recognised.
- Stress — chronic work, financial, or personal stress elevates cortisol, which suppresses testosterone and activates the sympathetic nervous system, both of which inhibit erectile function.
How it presents: ED that is situational rather than consistent — present with one partner but not another, or during partnered sex but not during masturbation. Preserved morning and nocturnal erections are the key clinical indicator: if morning erections are present, the vascular mechanism is intact and the cause is more likely psychological.
What helps: Psychosexual assessment and management. In purely psychological ED, addressing the anxiety, relationship dynamics, or underlying psychological factors frequently produces full recovery. Medical management can provide functional support while psychological work progresses. Where performance anxiety is the dominant driver, a sexual performance anxiety assessment is the right starting point. (Althof SE et al., Journal of Sexual Medicine, 2014)
3. Low Testosterone (Hypogonadism)
Testosterone is the primary driver of male sexual desire. When testosterone falls below optimal levels — whether through age-related decline, medical conditions, or other factors — libido is typically the first function affected, with ED frequently following.
Testosterone declines gradually from around age 30 — at approximately 1-2% per year. In some men this decline is clinically significant; in others it remains within acceptable range throughout life. Hypogonadism — defined as testosterone deficiency with associated symptoms — affects an estimated 2-6% of adult men, rising to 20-40% in men over 60. (Bhasin S et al., Journal of Clinical Endocrinology and Metabolism, 2010)
Beyond age-related decline, testosterone can be suppressed by obesity (fat tissue converts testosterone to oestrogen), chronic illness, pituitary dysfunction, and certain medications.
How it presents: reduced libido is typically more prominent than difficulty with erection itself. Associated symptoms include fatigue, reduced motivation, mood changes, difficulty concentrating, and reduced muscle mass. Blood testing is required to confirm.
What helps: where testosterone deficiency is confirmed on blood testing, appropriate hormonal management can significantly restore libido and improve erectile function — see our Low Libido & Sexual Wellness service. Blood testing is essential — testosterone replacement in men with normal testosterone levels is not clinically appropriate and carries risks.
4. Neurological Causes
Normal erectile function requires intact nerve pathways from the brain through the spinal cord to the cavernous nerves of the penis. Conditions that damage these pathways can cause or worsen ED:
- Multiple sclerosis — demyelination disrupts nerve signal transmission
- Parkinson's disease — affects autonomic nervous system function
- Spinal cord injury — depending on level and completeness of injury
- Peripheral neuropathy — most commonly associated with diabetes
- Stroke — depending on location and extent
Post-prostatectomy ED represents a specific and common form of neurogenic ED. The cavernous nerves responsible for erectile function run in close proximity to the prostate — even in nerve-sparing surgery, traction, thermal injury, or disruption of these nerves is common. An estimated 25-75% of men experience ED following radical prostatectomy, with the range reflecting variation in surgical technique, age, and pre-operative function. (Frey A et al., Journal of Sexual Medicine, 2014)
What helps: Penile rehabilitation following prostatectomy — using focal shockwave therapy, vacuum erection devices, and medical management — aims to support nerve recovery and maintain erectile tissue oxygenation during the 12-24 month recovery window. For other neurological causes, management depends on the specific condition and its severity.
5. Medication-Induced ED
A significant and frequently overlooked cause of ED is prescribed medication. The most commonly implicated drugs include:
| Class | Commonly implicated | Notes |
|---|---|---|
| Antihypertensives | Thiazide diuretics (e.g. bendroflumethiazide), beta-blockers (e.g. atenolol, propranolol) | ACE inhibitors and calcium channel blockers are less likely to cause ED and may be alternatives |
| Antidepressants | SSRIs (e.g. sertraline, fluoxetine, citalopram), SNRIs | Very commonly cause delayed ejaculation and ED. Bupropion is less likely to cause sexual dysfunction |
| Other medications | Finasteride, antiandrogens, opioid pain medications, H2 blockers, some antihistamines, antipsychotics | Mechanisms vary — reduced dihydrotestosterone, suppressed testosterone, or elevated prolactin |
How it presents: ED that began or significantly worsened following the introduction of a new medication. The temporal relationship is the key diagnostic clue.
What helps: discussion with the prescribing doctor about alternative medications. Never stop cardiovascular or other important medications without medical advice — the risk of the underlying condition must be weighed against the impact on sexual function. In many cases, switching to an alternative within the same drug class resolves or substantially improves the ED. A specialist urology consultation is the right setting to review this alongside your other causes.
6. Hormonal Causes Beyond Testosterone
While testosterone deficiency is the most common hormonal cause of ED, other hormonal abnormalities can contribute:
- Elevated prolactin (hyperprolactinaemia) — suppresses testosterone production and reduces libido. Can be caused by pituitary tumours (prolactinoma), antipsychotic medication, or hypothyroidism.
- Thyroid dysfunction — both hypothyroidism and hyperthyroidism can impair sexual function through effects on mood, energy, and cardiovascular function.
These are identified through blood testing — which is why a hormone panel (testosterone, LH, FSH, prolactin, thyroid function) is an important part of any comprehensive ED assessment.
7. Lifestyle Factors
Several modifiable lifestyle factors independently contribute to ED — and addressing them can produce meaningful improvement without any specific treatment:
- Obesity — associated with endothelial dysfunction, low testosterone, and cardiovascular risk. A 2004 JAMA study found that lifestyle intervention in obese men with ED produced significant improvement in erectile function scores — with one third recovering normal function without medication. (Esposito K et al., JAMA, 2004)
- Smoking — directly toxic to vascular endothelium. Smoking cessation is associated with improvement in erectile function — with the benefit more pronounced in younger men with shorter smoking histories. (Pourmand G et al., International Journal of Impotence Research, 2004)
- Alcohol — heavy chronic alcohol use suppresses testosterone production, damages peripheral nerves, and accelerates vascular disease. Moderate use within recommended limits is not significantly associated with ED.
- Sedentary behaviour — physical inactivity accelerates cardiovascular risk and is independently associated with ED. Regular aerobic exercise improves endothelial function and has been shown to improve erectile function. (Gerbild H et al., Sexual Medicine, 2018)
- Cycling — prolonged pressure on the perineum from cycling, particularly with narrow saddles, can compress the pudendal artery, causing temporary ischaemia of the penile vasculature. A recognised occupational cause of ED in committed cyclists, usually reversible with saddle modification and reduced cycling volume.
How to Identify Your Cause: What a Proper Assessment Involves
The cause of ED cannot be reliably identified without clinical assessment. Self-diagnosis based on symptoms alone is unreliable — the presentations overlap significantly. A proper specialist assessment for ED, such as a men's urology consultation, includes:
- Clinical history — duration of symptoms, whether ED is situational or consistent, presence of morning erections, cardiovascular risk factors, current medications, relationship context, and psychological history
- Validated scoring — the IIEF-EF (International Index of Erectile Function — Erectile Function domain) questionnaire provides an objective baseline severity score
- Blood tests — testosterone (total and free), LH, FSH, prolactin, thyroid function, fasting glucose, HbA1c, lipid profile — these identify hormonal, metabolic, and cardiovascular contributors
- Penile Doppler ultrasound — where indicated, this assesses penile arterial blood flow directly, the gold standard investigation for vascular ED
- Cardiovascular risk assessment — given the relationship between ED and cardiovascular disease, assessment of modifiable cardiovascular risk factors is an integral part of any ED evaluation
Cause and Treatment: A Summary
| Cause | How Common | Key Indicator | Treatment |
|---|---|---|---|
| Vascular disease | Very common (>50% over 40) | Progressive, worse with CV risk factors | Focal shockwave therapy, CV risk modification |
| Psychological | Common (most <40) | Situational, morning erections preserved | Psychosexual assessment, medical support |
| Low testosterone | Common (20-40% over 60) | Reduced libido, fatigue, mood changes | Hormonal management (if confirmed) |
| Neurological | Less common | Associated neurological condition or surgery | Penile rehabilitation, medical management |
| Medication-induced | Common (often missed) | Temporal link to new medication | Medication review with prescriber |
| Lifestyle factors | Very common contributor | Obesity, smoking, sedentary, alcohol | Lifestyle modification |
| Hormonal (other) | Less common | Identified on blood testing | Treat underlying hormonal condition |
Dr Kishore Bahl
Every ED assessment at Shockwave ReVibe Clinic is carried out personally by Dr Bahl — a full clinical history, IIEF-EF scoring, and honest guidance on which cause applies to you. Read our complete guide to ED treatment →
Frequently Asked Questions
What is the most common cause of erectile dysfunction?
Vascular disease — endothelial dysfunction of the penile arteries — is the most common cause in men over 40, accounting for the majority of ED presentations in this age group. Psychological factors are the most common cause in younger men.
Can stress cause erectile dysfunction?
Yes. Chronic stress elevates cortisol, which suppresses testosterone and activates the sympathetic nervous system — both of which inhibit erectile function. Acute stress and performance anxiety can cause situational ED in otherwise healthy men.
Can diabetes cause ED?
Yes — diabetes is one of the most significant risk factors for ED, affecting both the blood vessels (vascular ED) and the nerves (neurogenic ED) required for normal erectile function. ED affects an estimated 35-75% of men with diabetes. (Maiorino MI et al., Journal of Sexual Medicine, 2014)
Does low testosterone always cause ED?
Not always. Testosterone primarily drives libido (sexual desire) rather than erectile function directly. Some men with low testosterone maintain erectile function; others experience both reduced desire and difficulty with erections. Blood testing identifies whether testosterone deficiency is contributing.
Can medications cause ED?
Yes — several commonly prescribed medications cause or worsen ED, including certain antihypertensives (thiazide diuretics, beta-blockers), antidepressants (SSRIs), finasteride, and opioid pain medications. If ED began following a new medication, discuss alternatives with your prescribing doctor.
Is ED caused by age?
Age is a risk factor, not a cause. The prevalence of ED increases with age because the conditions that cause ED — vascular disease, hormonal changes, neurological conditions — become more common with age. ED itself is not an inevitable consequence of ageing and is treatable at any age.
How do I know if my ED is physical or psychological?
Morning and nocturnal erections are the key indicator. If regular morning erections are present, the vascular mechanism is largely intact and the cause is more likely psychological. Consistent absence of morning erections suggests a physical cause. A clinical assessment — including IIEF-EF scoring and blood tests — establishes this clearly.
Can lifestyle changes reverse ED?
In men where ED is primarily lifestyle-driven — obesity, smoking, heavy alcohol use, sedentary behaviour — addressing those factors can produce meaningful improvement. A 2004 JAMA study found that one third of obese men with ED recovered normal erectile function through lifestyle modification alone.
Do I need a GP referral to see a specialist?
No. At Shockwave ReVibe Clinic you can book directly without a GP referral. Initial consultation: £59. No waiting list.
What happens at an ED consultation?
Dr Bahl takes a comprehensive medical and psychosexual history, completes the IIEF-EF questionnaire, recommends relevant blood tests, and where indicated refers for penile Doppler ultrasound. All treatment options are discussed honestly based on the clinical findings — not just the treatments the clinic offers.
Clinical References
- Vlachopoulos C et al. (2010). Prediction of cardiovascular events and all-cause mortality with erectile dysfunction. Circulation, 121(22): 2377-2385.
- Esposito K et al. (2004). Effect of lifestyle changes on erectile dysfunction in obese men. JAMA, 291(24): 2978-2984.
- Althof SE et al. (2014). An update of the international society of sexual medicine's guidelines for the diagnosis and treatment of premature ejaculation. Journal of Sexual Medicine, 11(6): 1392-1422.
- Bhasin S et al. (2010). Testosterone therapy in men with androgen deficiency syndromes. Journal of Clinical Endocrinology and Metabolism, 95(6): 2536-2559.
- Frey A et al. (2014). Low-intensity extracorporeal shockwave therapy in the treatment of postprostatectomy erectile dysfunction. Journal of Sexual Medicine, 11(12): 2960-2967.
- Pourmand G et al. (2004). Do cigarettes cause erectile dysfunction? International Journal of Impotence Research, 16(3): 269-273.
- Gerbild H et al. (2018). Physical activity to improve erectile function: a systematic review of intervention studies. Sexual Medicine, 6(2): 75-89.
- Maiorino MI et al. (2014). Lifestyle modifications and erectile dysfunction: what can be expected? Journal of Sexual Medicine, 11(6): 1449-1462.
- European Association of Urology (2024). EAU Guidelines on Sexual and Reproductive Health. EAU Guidelines Office, Arnhem, The Netherlands.
Dr Kishore Bahl is a Specialist Grade Doctor in Urology (GMC Registration: 6070860) and founder of Shockwave ReVibe Clinic, 22 Notting Hill Gate, London W11 3JE. To book a consultation, call 020 3004 0564 or visit shockwave-revibe.co.uk.
Last reviewed: August 2026