Side Effects of Antidepressants

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Author: RxISK Medical Team

Last updated: 2016

Other guides are available in Guides & Papers.

Antidepressants can cause a range of physical, emotional and psychological side effects. Some may be present within the first few hours of starting treatment, whereas others may develop over the longer-term. They can range from minor problems through to serious issues that can be life altering or life threatening.

Some side effects – usually those that produce a clear physical effect – will likely be more obvious as being caused by the medication. But others may be mistaken for the worsening of an illness, particularly where the problem occurs gradually over a period of time.

Antidepressants can also leave problems after stopping treatment. Some side effects are not always completely reversible and may remain indefinitely. It is important to consider these risks when making a decision about your treatment.

Obvious side effects of antidepressants:

Side effects that may feel like the worsening of an illness:

Special conditions:

Akathisia (restlessness, agitation & turmoil)

Akathisia on antidepressants may occur within hours of starting treatment or take weeks to appear. It is a complex side effect of various psychiatric drugs, and is often described as a sense of inner restlessness.

It can manifest as a physical discomfort or inability to remain still, but it can also be less obvious, presenting as anything from a constant and disturbing unease in the mind, through to an intense emotional turmoil.

See our main page on akathisia.

Aggression

Up to 1 in 100 people will become aggressive on an antidepressant. This may lead to violent behavior.

Alcohol

SSRIs can cause an intense craving for alcohol, which can escalate into full-blown alcoholism. This is not usually present from the first dose but develops over weeks or months. Few people realize this can happen and as a result doctors will usually try to keep the person on their antidepressant in the belief that it may stem from an underlying depression, when in fact stopping the antidepressant can clear up the problem within days.1

SSRIs also appear in some people to raise blood alcohol levels in ways that are not currently understood, so the person may be more drunk than they expect.

Confusion

An individual may become confused or disorientated, and as a consequence, quite agitated in a way that puts them at risk to themselves or to others.

Dissociative experiences

Dissociative experiences refer to unusual changes in perception and feelings, often involving a sense of detachment.

Antidepressants can cause a number of dissociative experiences including:

  • Amnesia
  • Déjà vu
  • Depersonalization
  • Derealization
  • Hallucinations
  • Prominent nightmares or lucid dreaming

Depersonalisation is an experience of feeling strange and unusual, almost as though you are not really yourself anymore, or that you are in a kind of a dream or haze.

Derealisation refers to a similar set of feelings and perceptions, but in this case it is the world itself that seems strange or unreal; everything may seem far away or staged in some way – as though life is being watched rather than lived.

Depersonalisation and derealisation are relatively common on antidepressants.

Dry mouth

Dry mouth can happen with almost all antidepressants, and in most cases is usually a minor side effect. However, with long-term use the lack of saliva can result in increased tooth decay.

Emotional blunting

Most people who take an SSRI or similar antidepressant will experience a degree of emotional blunting. Some people notice that they are unable to cry or that they no longer care as much about things that were previously important to them. Feelings of love and attachment towards a partner may be affected.

People often do not realize the extent to which they are affected until they stop treatment. However, the problem does not always completely resolve and may persist after treatment is stopped.

In some cases, emotional blunting can result in disinhibited behavior. A person may say or do things that are out of character or that may be deemed inappropriate.

Fainting

Tricyclic antidepressants, MAOIs and mirtazapine all lower blood pressure. On treatment, changes of posture such as getting out of bed or standing up from a chair could cause a significant drop in blood pressure leading to falls, especially in older individuals.

Fractures

SSRIs are associated with a higher incidence of bone fractures than older drugs. There is an increased risk of fractures for years after stopping treatment.

Gastrointestinal issues

SSRIs are significantly more likely to cause nausea and indigestion than other antidepressants, but all can cause a range of gastrointestinal and digestive issues including:

  • Bloating
  • Constipation
  • Indigestion
  • Nausea
  • Vomiting

Problems such as nausea and vomiting are usually more common when starting or stopping an antidepressant. Others like bloating and indigestion may be present over the longer-term.

Gastrointestinal and digestive issues can sometimes remain after stopping treatment, and may be mistaken for Irritable Bowel Syndrome (IBS).

Headache

Headaches that are caused by antidepressants typically feel muzzy (blurred, indistinct) compared to normal headaches. In rare cases, antidepressants may trigger migraines.

Haemorrhages

SSRIs and similar drugs can increase the risk of bleeding. It may be into the stomach, womb, or brain in the form of a stroke. Care must be taken when combining SSRIs with other drugs that also have this effect, such as aspirin and other non-steroidal analgesics.

Manic or psychotic reactions

Antidepressants can cause manic reactions in which an individual may become hyperactive with feelings of euphoria or racing thoughts. Manic reactions on antidepressants are sometimes misdiagnosed as bipolar disorder.

In the case of psychosis, a person’s thoughts and emotions are distorted to the point that they lose contact with reality. They may be paranoid, or have bizarre ideas or delusions. In such a state, there is a risk that they may harm themselves or others without realizing what they are doing.

Manic or psychotic reactions to antidepressants are now one of the most common causes of admission to a psychiatric unit.

Palpitations & cardiac issues

Palpitations are an awareness that the heart is beating harder or faster than normal, or that it is skipping a beat. It may also feel like a fluttering sensation in the chest. Although very unsettling, palpitations are usually harmless.

However, most psychotropic drugs including antidepressants can also have direct effects on the electrical conduction of the heart, especially by lengthening the QT interval. This can be a problem if the dose is increased, or in those people who were born with longer QT intervals to begin with. It is also an issue when a person is put on a combination of drugs where each drug has this effect, leading to a dangerous increase.

Pregnancy

Antidepressants double the underlying rate of birth defects and miscarriages, and increase the risk of development delay in children. There is a risk of birth defects for months or perhaps longer after stopping treatment.

It is a common misconception that depression causes birth defects. This is not the case.

Stopping an antidepressant may require a slow reduction over many months due to withdrawal symptoms. This creates a serious problem for women of childbearing years who are on antidepressants and unexpectedly become pregnant.

Infants born to mothers on antidepressants can experience a withdrawal syndrome at birth. All antidepressants transfer into breast milk.

Sedation

Antidepressants can cause drowsiness and feelings of fatigue. This may affect driving or other tasks where full concentration is required.

Sensory neuropathy

It is becoming clearer that almost all psychotropic drugs can cause peripheral neuropathies. The classic symptom of this is burning feet (causalgia). Hands, mouth and other parts of the body can also burn or just be painful. Other features include a variety of bizarre sensations around the body, or sensations of pain on temperature change or gentle touch.

Some people on SSRIs notice a generalized reduction in skin sensitivity across the entire body.

Linked disturbances include tinnitus, visual disturbances like visual snow, altered sense of smell, altered taste perception and temperature dysregulation.

Sensory disturbances can sometimes persist after the drug has been stopped.

Serotonin syndrome

Serotonin Syndrome is a potentially fatal condition which is believed to result from an excess of serotonin. SSRIs alone may cause the problem but are more likely to do so if combined with other drugs that also act on the serotonin system.

It is usually characterized by a combination of symptoms including:

  • Confusion, agitation and restlessness
  • Diarrhoea
  • Muscle twitches and tremors
  • Over-responsive reflexes
  • Shivering and sweating

Sexual side effects

Close to 100% of people who take an antidepressant will experience some degree of sexual side effects. Depending on the drug, this can include:

  • Reduced genital sensation
  • Loss of libido (sex drive)
  • Erectile/lubrication dysfunction
  • Delayed or blocked orgasm
  • Reduced feeling of pleasure during orgasm

Sexual side effects do not always completely resolve after stopping treatment and may persist indefinitely. See information on Post-SSRI Sexual Dysfunction (PSSD).

Antidepressants can also cause Persistent Genital Arousal Disorder (PGAD). This is a relentless and uncomfortable feeling of arousal in the genitals, but without any accompanying feeling of desire.

On stopping antidepressants, some men develop premature ejaculation.

Other problems in men

  • Priapism (sustained erection). This may be painful and last for several hours. It requires urgent medical attention.
  • Retrograde ejaculation – Semen flows backwards into the bladder instead of out through the urethra.

Other problems in women

  • Disruption to menstrual cycle
  • Change in breast size and/or tenderness

Suicide

Antidepressants can cause suicidal thoughts and feelings, even in healthy volunteers. It can affect people of any age. Up to 1 in 100 people will engage in a suicidal act. The most dangerous periods are when starting the medication, changing the dose, and shortly after stopping.

The sudden emergence of drug-induced suicidal thoughts is sometimes mistaken to mean that the person is becoming more ill. This can lead to the dose being increased or more medication being added, ultimately resulting in a suicidal act.

It is often said that antidepressants increase the risk of suicide by giving a person the energy to act upon their suicidal thoughts before their depression has lifted. However, given that completely healthy people without any mood disorders can be made suicidal on antidepressants, this would appear to be incorrect.

In 2000, a healthy volunteer trial was carried out to investigate the differences in emotional side effects between sertraline and reboxetine. 20 healthy volunteers were recruited from the medical, nursing, and administrative staff at a general hospital psychiatric unit. To the surprise of the trial coordinators, 2 of the staff became suicidal on sertraline. One began fantasizing about hanging herself from a beam across the bedroom ceiling. The second developed an irresistible thought that she must kill herself violently by throwing herself beneath a car or train, and had to be placed under observation.2

Sweating

It is not uncommon for antidepressants to produce an increase in sweating. This is particularly common in hot weather. It may be most noticeable at night, leading to people waking up to find their sheets drenched.

Teeth grinding and jaw clenching

Some antidepressants, in particular the SSRIs, may lead to tooth grinding. Sometimes this problem can persist after the drug is stopped.

Tremors and muscle twitching

Some people on an antidepressant may have a tremor of their hand or arm. This is most common on high doses, and may mean that the dose needs to be lowered.

All antidepressants can cause twitches or jerky movements (myoclonus) of the head, arms or legs. These are most common in the legs at night, but may affect any part of the body at any time. It happens in up to 10% of cases.

Urinary difficulties

Most antidepressants can cause trouble with urination. This can range from a slight delay before passing water, through to significant urinary retention. Both men and women can be affected, and urinary problems can sometimes persist after stopping treatment.

It is often stated that urinary retention on antidepressants is caused by their anticholinergic effects. This is incorrect. It is actually due to their actions on the catecholamine system.

Vision problems

Blurred vision is a side effect of most antidepressants, and can sometimes persist after stopping treatment.

Antidepressants can also increase pressure in the eyes which may be a problem for those who are susceptible to glaucoma.

Weight gain

Successful treatment of depression may restore appetite and therefore be expected to lead to some weight gain. But antidepressants can also cause significant weight gain as a side effect, in some cases up to 10 kg, without any change in diet, lifestyle or exercise regime.

Withdrawal

Depending on the antidepressant, up to 50% of people may have withdrawal difficulties. Depressive symptoms and feelings of anxiety are the most common withdrawal side effects. These are often mistaken for the return of an illness.

Antidepressants often need to be tapered slowly over a number of months using a liquid version of the drug. Around 1 in 16 people will be unable to stop even with tapering, due to intolerable withdrawal symptoms.

There can also be long-term problems after stopping.

For more information about withdrawal, see Stopping Antidepressants.

Further reading

Footnotes

1 Brookwell L, Hogan C, Healy D, Mangin D (2014). Ninety-three cases of alcohol dependence following SSRI treatment. Int J Risk and Safety in Medicine 26, 99-107.

2 Healy D. Emergence of antidepressant induced suicidality. Primary Care Psychiatry, 2000 6:23–28.