Meet your 2021 Best of the Best Pharmacy Award winners! Read more >
Skip to main content

Going on antidepressants: A beginner’s guide to side effects

If you, like me, suffer from moderate to major depression, chronic anxiety, or even bipolar disorder, it’s likely your medical provider prescribed you an antidepressant medication. I can tell you from experience that these drugs can be life-changing. Together with talk therapy, antidepressants can treat the symptoms that keep you from living a full life. They can free you from deep sadness, fear, irritability, and the many other manifestations that interfere with work, school, and personal relationships.

There are several classes of antidepressant drugs, and they all work in different ways. But one thing they have in common is that they alter the presence of certain chemicals in your brain. This is a good thing, in many ways, as it helps to treat your depression or anxiety. But like all medications, it can cause side effects as well.

A team of physicians and pharmacists helped to create this comprehensive guide to antidepressant medication and the side effects of antidepressants.

What are the types of antidepressants?

Antidepressants are prescription medications that treat the symptoms of clinical depression, some anxiety disorders, seasonal affective disorder, and dysthymia (or mild chronic depression). All of them work by correcting chemical imbalances of neurotransmitters in the brain that are associated with changes in mood and behavior.

“Different antidepressants target different neurotransmitters in the brain and nervous system,” says Justin Hall, MD, a clinical psychiatrist with Spectrum Behavioral Health in Annapolis, Maryland. “Serotonin is the most commonly targeted neurotransmitter that has been associated with anxiety and depression.”

Serotonin is targeted because it is the neurotransmitter that is most commonly associated with depression. This chemical has a wide variety of functions in the human body. Many doctors and laypeople call it the “happy chemical,” because it is known to increase happiness and a sense of wellbeing. But it can also affect your digestion, bowel movements, memory, sleep, and many other factors.

The classes of antidepressant drugs include:

  • Selective serotonin reuptake inhibitor (SSRI)
  • Serotonin-norepinephrine reuptake inhibitor (SNRI)
  • Tricyclic antidepressant (TCA)
  • Monoamine oxidase inhibitor (MAOI)
  • Serotonin antagonist and reuptake inhibitor (SARI)
  • Atypical antidepressant

“Each of these classes, and even the drugs within them, affect the levels of various neurotransmitters to a different degree,” says Alam Hallan, Pharm.D., director of pharmacy for Guelph General Hospital in Ontario, Canada.

For this reason, all patients need an individualized treatment plan. “The best agent for a particular patient is what works best for them,” Dr. Hallan says. “Most patients usually start with SSRIs or SNRIs. If they do not respond to those drugs, then they can try TCAs or atypicals. MAOIs are reserved for very resistant cases due to some severe interactions.”

Selective serotonin reuptake inhibitors (SSRIs) and Serotonin-norepinephrine reuptake inhibitors (SNRIs)

Both SSRIs and SNRIs are prescribed to treat depression and some anxiety disorders. They work by targeting chemicals in your brain called neurotransmitters. When your brain sends messages from one cell to another, such as “feel happy about this news,” or “this movie is funny,” those messages travel with the help of neurotransmitters.

SSRIs target a neurotransmitter called serotonin, and SNRIs target both serotonin and norepinephrine. Normally, when your brain sends messages from one neuron to another, the “sender” emits a bit of neurotransmitter to carry the message, then it reabsorbs the neurotransmitter after the message is delivered.

SSRI antidepressants work by blocking the reabsorption (or reuptake) of serotonin in your brain, after it delivers its happy messages. Therefore, your brain will have more serotonin available to deliver more happy messages. The most commonly prescribed antidepressants, SSRIs are considered the most effective with the fewest side effects. Some examples include Celexa (citalopram), Lexapro (escitalopram), Paxil (paroxetine), Prozac (fluoxetine) and Zoloft (sertraline).

Similarly, SNRIs increase the levels of both serotonin and norepinephrine in your brain.

Norepinephrine is another neurotransmitter that plays a role in stabilizing mood. Some examples of SNRIs include Cymbalta (duloxetine), Effexor (venlafaxine), and Pristiq (desvenlafaxine).

Tricyclic antidepressants (TCAs)

Tricyclic (or tetracyclic) antidepressants were some of the earliest antidepressants developed. They are pretty effective, but they also come with a number of side effects, so they are largely replaced with newer medications unless SSRIs or SNRIs don’t work.

Cyclic antidepressants also block the reuptake of the neurotransmitters serotonin and norepinephrine, increasing the levels of these two chemicals in the brain. However, TCAs can affect other neurotransmitters as well, which is why they have so many more side effects. Examples of TCAs include amitriptyline and amoxapine.

Monoamine oxidase inhibitors (MAOIs)

Like the others, monoamine oxidase inhibitors (MAOIs) work by affecting neurotransmitters. Specifically, MAOIs affect dopamine, serotonin, and norepinephrine, which collectively are known as monoamines. There is also a chemical in the brain called monoamine oxidase, which removes those neurotransmitters. MAOIs work by inhibiting monoamine oxidase, therefore allowing more of those neurotransmitters to stay in the brain.

These were the very earliest antidepressants, developed in the 1950s. They were effective at treating major depressive disorders. However, like TCAs, they come with a lot of side effects. There are a number of dangerous drug interactions between MAOIs and other drugs, making it difficult to treat people who have mental health problems along with other medical conditions. Some examples include Nardil (phenelzine) and Marplan (isocarboxazid).

Serotonin antagonist and reuptake inhibitors (SARIs)

Serotonin antagonist and reuptake inhibitors (SARIs) are FDA-approved as antidepressant medications, but they are more commonly used off-label as sleep aids. Like SSRIs, they work by inhibiting serotonin reuptake. But they also act as antagonists, inhibiting a particular serotonin receptor called 5HT2a, which blocks the function of a serotonin transporter protein.

Some examples of SARIs include Desyrel (trazodone) and Serzone (nefazodone).

Atypical antidepressants

Atypical antidepressants are just like they sound—not typical. This means that they don’t fit into any of the other classes of antidepressants, and they work in unique ways. Though there isn’t a way to sum up how these drugs work, suffice it to say that they all change the makeup of certain neurotransmitters in your brain, including dopamine, serotonin, and/or norepinephrine. Some examples of atypical antidepressants are Wellbutrin (bupropion) and Remeron (mirtazapine).

Understanding side effects of antidepressants

While there is a wide range of side effects that taking antidepressant medications can cause, these are the most common:

  • Weight loss or gain
  • Sexual problems, including loss of sexual desire, erectile dysfunction, and others
  • Insomnia
  • Drowsiness
  • Fatigue
  • Headaches
  • Nausea
  • Dry mouth
  • Blurred vision
  • Constipation
  • Dizziness
  • Agitation
  • Irritability
  • Anxiety
  • Irregular heartbeat

In addition to these, there are long- and short-term side effects of antidepressant medications.

Long-term side effects of antidepressants

While most antidepressant side effects are short-term, there are a few that last longer—these adverse effects are rarer and can often be managed in a number of ways, detailed below. The potential long-term side effects include weight changes, sexual problems, insomnia, drowsiness, and fatigue.

Weight gain

The reason for weight gain while taking antidepressants long-term is unclear. “It could be that patients who once ate very little while they were depressed experience their appetite returning with therapy,” Dr. Hallan suggests, “or the medications might cause a change in their metabolism. In most cases, it averages to about five pounds or so per year.”

Some medical studies have shown that long-term use of antidepressants can increase your risk of illnesses related to weight gain, such as type 2 diabetes.

If managing this side effect with diet and exercise doesn’t work, Dr. Hallan suggests trying a new medication. All of these drugs work differently in different people, so one medication might not cause the same side effects in everyone, even if it is commonly known to cause that particular side effect.

Sexual dysfunctions

“Sexual side effects are generally a common side effect that can lead to people stopping their medications even though they are doing well on the medication,” Dr. Hall says.

In fact, as many as half of all patients taking SSRIs might experience some sexual side effects, including decreased sex drive, decreased ability to have an orgasm, vaginal dryness, or erectile dysfunction.

While other side effects are short-lived, these sexual side effects can persist throughout the entire time the patient is taking antidepressants. However, they shouldn’t be debilitating or dangerous. If they are bothersome to the point where you’d prefer not to take the medication, Dr. Hall recommends speaking with your prescribing doctor about reducing the dosage, taking the medicine at a different time of day, or switching to a different medication.

Sleep problems

Varying from drug to drug and patient to patient, many antidepressants cause difficulty with sleep—either insomnia or drowsiness. If you experience this side effect, Dr. Hall recommends timing your medications according to how they affect your sleep: If your antidepressant makes you drowsy, take it before bed. If it keeps you awake, take it in the morning. Typically, the wakefulness or sleepiness effects of the drug will wear off after several hours.

Short-term side effects of antidepressants

While many people are symptom free on antidepressants, it’s not abnormal to experience short-term side effects that last a few days or a few weeks. These might include nausea, headaches, dry mouth, blurred vision, constipation, and anger or irritability.


Nausea occurs in about 25% of antidepressant patients. It usually starts immediately after initiating treatment and wanes after about two or three weeks. However, it persists throughout treatment in about one-third of those people. Nausea is more common with venlafaxine and SSRIs than with the atypicals like bupropion, mirtazapine, or reboxetine. It can typically be managed by taking your meds on a full stomach.


A study published in the journal Clinical Therapeutics found that headaches were the most common side effect of 40,000 people who recently started taking antidepressants. Those who took TCAs and SSRIs were more likely than those who took SNRIs or bupropion to experience headaches. However, many people do build up a tolerance for these side effects, and they go away after a short time.

Dry mouth

Experiencing dry mouth? This might be because the drugs briefly inhibit your body’s production of saliva. TCAs are more likely to cause dry mouth than SSRIs.

Dr. Hallan recommends sucking on ice chips, taking frequent sips of water, chewing gum, using mints, or brushing your teeth.

Vision problems

People with blurred vision describe it as a lack of sharpness or clarity to their vision. Blurred vision is most common with TCAs. People might also experience burning, itching, and redness of the eye, or a gritty sensation in the eye. In addition, some people say their eyes are more sensitive to light.

If you are taking antidepressants and you experience blurred vision, first get an eye exam to rule out other vision problems. You might also try using eye drops and a humidifier to moisturize your eyes. Talk to your provider about changing your dose if this side effect persists beyond a few weeks.


The neurotransmitter serotonin has a number of functions aside from making you feel happier—it can affect your bowel movements, too, because serotonin is present in your gut. Sometimes, certain SSRIs and TCAs can cause constipation in the short-term. Patients can manage it by using laxatives, drinking plenty of water, and eating more fiber.


Dizziness is more common with TCAs and MAOIs than with other classes of antidepressants. The reason these meds sometimes cause dizziness is because they might lower your blood pressure. Dr. Hall recommends taking your medication at bedtime to help control this side effect.

Irritability or anxiety

Both irritability and anxiety are fairly rare side effects of antidepressants, but they do occur in a small number of patients. The reason is probably related to serotonin. As already noted, low levels of serotonin in the brain can lead to both depression and anxiety, which is why these medications all work to increase serotonin levels in some way. In the early days of treatment, your body is working on adjusting your serotonin levels, which causes them to fluctuate. This might cause a short bout of increased anxiety or irritability. As your serotonin levels become more steady, these symptoms should subside.

Side effect SSRI SNRI TCA MAOI SARI Wellbutrin Remeron
Weight gain X X X X X
Sexual dysfunction X X X X X
Sleep problems X X X X X X X
Nausea X X X X X X X
Headache X X X X X X X
Dry mouth X X X X X X X
Vision problems X X X X X X X
Constipation X X X X X X
Dizziness X X X X X X X
Irritability X X X X X X
Anxiety X X X X X X
Excessive sweating X X X X
Urine retention X X X
Low blood pressure X X X X

Serious side effects of antidepressants

Thus far, all of the common side effects we’ve discussed are relatively harmless, even if they are bothersome. There are, however, a few very rare, but also very serious, side effects that may occur when taking antidepressants. They include suicide, serotonin syndrome, and hyponatremia.

Fortunately, these dangerous side effects are very uncommon, and the risks are greatest in the first month of treatment.

Thoughts of suicide

For the most part, antidepressants help reduce all symptoms of depression, including suicidality. However, a small number of vulnerable patients—usually young adults—experience a high risk of increased suicidal ideations.

According to Dr. Hallan, this only happens in very specific scenarios. For example, a severely depressed person who is unmedicated might be experiencing suicidal thoughts. But his depression symptoms almost protect him from acting on those thoughts because they also cause him to feel extreme fatigue and loss of energy. Once he begins treatment, his energy and fatigue might improve just enough to give him the energy to follow through on his suicidal ideations.

In order to avoid this side effect, you should share any suicidal thoughts you have had with your healthcare provider before beginning treatment.

Serotonin syndrome

“Serotonin syndrome is a life-threatening medical emergency that happens in a very small number of patients,” says Dr. Hallan. “It is a particular risk for those who are on more than one serotonergic medications.” The group of symptoms include agitation, shivering, sweating, and hyperthermia. Taking certain supplements, like St. John’s Wort, can increase the risk of this condition.

If you experience these symptoms while taking an antidepressant, seek medical help immediately. They will discontinue your meds, give reversal agents, and help to manage your symptoms.


“Hyponatremia is another dangerous side effect and is seen in about 1 in 2,000 patients taking SSRIs,” Dr. Hallan explains. Referring to the lack of sodium in the blood, hyponatremia “is thought to be due to increased production of the diuretic hormone, which makes the body retain more water, thus diluting the amount of sodium in the body,” he says. Patients, particularly older patients, who are at risk should be monitored using a lab test.

Antidepressant withdrawal symptoms

Unless you are experiencing a dangerous side effect of antidepressants and have consulted your doctor, it is not a good idea to stop using them cold turkey. Discontinuation of antidepressants could trigger withdrawal symptoms, such as:

  • Anxiety
  • Insomnia or vivid dreams
  • “Head buzzing”
  • Headaches
  • Dizziness
  • Tiredness
  • Flu-like symptoms
  • Nausea
  • Irritability

If you must stop using antidepressants, or even change your dose, it is essential that you talk to your provider first. He or she can give you a schedule to wean yourself off of the medication so that you can minimize withdrawal symptoms.