What causes erectile dysfunction? Mojo’s rundown

Written with
Dr Matthew Chan

When our founders started struggling with erectile dysfunction (ED), they couldn’t find a rundown of all the things that could be causing it in one place.

So we thought: “why not do it ourselves?” and put together a pretty comprehensive list of the most common erectile dysfunction causes below.

But first, let’s start with the basics: understanding how you get an erection in the first place.

How do erections work? It’s a chain reaction

When your erections come easily, this is what’s going on:

  1. Your brain senses that sex might be on the cards.
  2. It increases your heart rate and blood flow to your penis.
  3. Messages travel down your nerves to tell the muscle at the bottom of the penis to tighten – this holds the blood in.
  4. You get an erection.

You may have already guessed that anything that gets in the way of these steps can trigger ED.

And you’re 100% right.

Let’s unpack those physical and psychological barriers. You will start to see how they mirror our 30-second biology lesson above.

Psychological factors

Sex can’t begin until the brain sends those all important first signals. When erection problems start in your head, it’s called psychological erectile dysfunction.

Common causes of psychological ED include:

  • performance anxiety
  • depression and anxiety
  • general stress
  • body issues and insecurities
  • boredom or lack of desire
  • an unhealthy relationship with porn
  • relationship problems
  • loss of sex drive/libido
  • lack or loss of confidence
  • eating disorders
  • sleep disorders or just general tiredness

Psychological causes of ED are very common.

Our expert, Kate Moyle, will tell you that every man who has had trouble getting it up will have something psychological about their problem, even if it’s just a contributing factor.

“Once you’ve had any reason to doubt your erections, negative thoughts can creep in. These can wreck your chances of getting hard, even if the initial cause of your ED has gone. It becomes a self fulfilling prophecy.”

Kate Moyle, Psychosexual Therapist

Conditions that affect blood flow and circulation to the penis

Blood flow can be impacted by vascular conditions (ones that affect the blood vessels).

These vascular conditions have all been recognised as common causes of erectile dysfunction:

  • heart disease (like coronary artery disease – where the arteries in the heart become clogged)
  • heart surgery
  • high blood pressure (also known as hypertension)
  • atherosclerosis (clogged blood vessels)  
  • diabetes
  • high cholesterol
  • being overweight/obesity
  • peripheral vascular disease (this affects the blood vessels as they send blood to the arms, hands, legs, and feet)
  • metabolic syndrome (a condition involving increased blood pressure, high insulin level, and body fat around the waist)
“If the blood supply to the penis becomes blocked, or the pathways that carry the blood get too narrow, it can be difficult, or even impossible, to get an erection.”

Silva Neves, Psychosexual and Relationship Therapist

Problems with the nervous system

If the nerves responsible for sending messages downstairs become damaged, your penis can’t get hard. It literally didn’t get the memo.

Before you read on, bear in mind that most of these conditions are extremely rare (especially in younger men).

These central nervous system conditions are often associated with ED:

Injuries or traumas

These can include:

  • injury to the penis, testicles, brain, spinal cord, prostate, bladder or pelvis
  • pelvic or prostate surgery
  • radiation therapy in the pelvic area
  • pelvic trauma
  • cycling (look for the numb penis)

Hormone imbalance

Our hormones act as chemical messengers in the body. It’s their job to pass information from one set of cells to another.

Hormones play an important role in both wanting sex and being able to have it.

Typical hormonal imbalances that can cause ED:

  • low testosterone levels can impact both sexual desire and blood flow
  • high prolactin levels can trigger headaches, low libido, and ED
  • abnormal thyroid levels can trigger low mood, fatigue, and low sex drive

Hormone replacement therapies can also trigger ED.


Some of the following medications can cause ED in some people (ready yourself for a lot of big words):

  • antihypertensives (meds for high blood pressure)
  • antihistamines
  • many antidepressants
  • diuretics (meds that cause increased urine flow)
  • antiarrhythmics (drugs for irregular heart function)
  • tranquillisers and sedatives
  • muscle relaxants
  • some anti-inflammatory drugs
  • anti-anxiety medication
  • stomach ulcer meds
  • hormone treatments
  • chemotherapy medication and some cancer drugs
  • prostate treatment drugs
  • opioid painkillers
  • anti-seizure medications
“If you think your medications are causing sexual problems, sometimes alternatives can be found that don’t have these side effects. Chat to your doctor to discuss your options.

It’s also important not to change or come off any planned medication before getting their advice.”

Dr Matthew Chan, Medical Doctor

Drink, recreational drugs, and ED

It’s no secret that drugs and drink can lower inhibitions and fuel sex. However, they can also pave the way for erection problems.

They both alter the way your mind and body works, which can lead to temporary or longer-lasting bouts of ED.

Alcohol can make you feel hornier, but it slows the messaging down, and can have a numbing effect on the penis, making it harder to get an erection in the moment. Heavy drinking over time can do more lasting damage too – making ED more likely.

Recreational drugs include both  party drugs and medications when they’re used to get high, including:

  • amphetamines (drugs like Speed and MDMA) can cause the blood vessels to narrow, stopping the blood from reaching the penis
  • cocaine can have the same effect as Speed
  • barbiturates (types of depressants or sedative drugs) can decrease sex drive
  • marijuana might increase arousal but prevent the smooth muscle in your penis from relaxing enough to let blood flow in
  • heroin and other opioids can lower testosterone and your interest in sex
  • ketamine stimulates the central nervous system and can potentially lead to vascular erectile dysfunction. If that wasn’t enough, it can also ruin your urethra and bladder
  • nicotine can decrease sex drive and harden blood vessels in the penis which need to stretch and swell

Life events

Periods of psychological and physical stress can put you under more pressure than you realise.

Your body may well de-prioritise sex until things feel calmer during these times:

  • going through a divorce or breakup
  • cheating and infidelity (both if you’ve been cheated on, or if you’re doing the cheating)  
  • taking part in threesomes or sex parties (that’s a lot of extra pressure!)
  • being in a polyamorous relationship (multiple partners)
  • when trying to conceive or going through IVF (both can put couples under a lot of stress)
  • entering a new relationship, it’s too damn exciting!
  • going on dates and having casual hook-ups
  • grief and loss, it takes a lot out of us
  • travel and jet lag, it’s exhausting whizzing around in metal tubes
  • feeling unwell or sick (like having a fever, the flu or the common cold), sex is the last thing on our minds when we’re reaching for the tissues

ED and age  

Although the chance of ED does increase with age due to the growing risk of vascular conditions, it’s by no means guaranteed.

Likewise, psychological ED is widely considered a leading cause of ED in young males.

But we’ve met lots of men of all ages whose experience with ED isn’t so easy to categorise.

The truth is, ED can impact you at any age (one study found 26% of men under 40 were impacted by ED) for all the reasons we list here.

But you can do things to minimise the risks.

And finally, phimosis and ED

Some men encounter ED when the foreskin is too tight to be pulled over the head of the penis. This is known as phimosis.

Phew! We got to the end

We covered a lot here, and maybe some of it struck a chord.

If you’re getting that “sounds a lot like me” feeling, you can find out more by:

Mojo is a safe space where guys can talk openly and anonymously about sexual issues and get expert help to reclaim their erections.  

You can access Mojo wherever and whenever you like. We’re always here.

Mojo aims to provide useful wellbeing resources to its users; however, you should not solely rely on opinions or advice available on the Website or given by the Community. Always seek advice from a qualified medical doctor or other healthcare professional before acting.

Start your 7-day free trial

Get unlimited access to Mojo and start your journey to better erections.

Try Mojo for free

Press enquires:

Anything else:

Mojo, 15 Westland Pl, London, N1 7LP

Help is available when you're feeling low – you don't have to suffer in silence. If you're in crisis or struggling to cope, find someone to talk to on Find a Helpline.