Explainer: As mental health challenges rise, here is what you need to know about antidepressants

A recent study has highlighted potential physical health risks associated with commonly prescribed antidepressants.

Antidepressants are prescribed primarily to treat mental health conditions that affect mood, thinking, and behaviour.

According to the World Health Organisation (WHO), they are used to manage disorders such as depression, anxiety disorders, post-traumatic stress disorder (PTSD), obsessive-compulsive disorder (OCD), chronic pain, sleep disorders, and sometimes eating disorders.

They work by influencing neurotransmitters, chemicals in the brain that regulate mood, emotions, and stress response, helping to restore balance and improve symptoms.

Mental health challenges are a growing concern both globally and in Kenya, highlighting the increasing need for treatments such as antidepressants.

WHO says that in 2019, an estimated 970 million people worldwide were living with a mental disorder, with anxiety and depression being the most common.

Anxiety disorders alone affect roughly 4.4 per cent of the global population, and nearly one-fifth of people worldwide reported experiencing anxiety or depression for more than two weeks in 2020.

In Kenya, mental and neurological disorders are among the most common health conditions. About 11 per cent of seemingly healthy Kenyans have a diagnosable mental disorder, and up to 30 per cent of patients seen in outpatient health facilities present with a mental health condition.

The prevalence of common mental disorders in the general population is estimated at 10.8 per cent, with depression and anxiety accounting for 6.1 per cent. Despite the high need, mental health services in Kenya are under-resourced, with five out of six Kenyans lacking access to a psychiatrist.

National data indicate that up to 25 per cent of outpatients in health facilities may have a mental health condition, while approximately 1 per cent of the population may experience psychosis.

Effects of medications

The research, published in The Lancet conducted by teams from King's College London's Institute of Psychiatry, Psychology & Neuroscience and the University of Oxford, and identified clinically significant changes in body weight, heart rate, cholesterol levels, and blood pressure among patients taking these medications.

The study reviewed 151 studies and 17 US Food and Drug Administration reports, involving over 58,500 patients. It compared 30 commonly used antidepressants with placebos over an average treatment period of eight weeks.

Findings showed that certain antidepressants were associated with weight gain of up to two kilograms, while others led to weight loss.

The difference in average weight change ranged from a 2.5-kilogram loss with agomelatine to a 2-kilogram gain with maprotiline. Nearly half of the patients on maprotiline or amitriptyline experienced weight gain, whereas over half of those taking agomelatine lost weight.

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Weight gain was most pronounced with medications that antagonise histamine H1 and serotonin 5-HT2C receptors, such as mirtazapine and several tricyclic antidepressants.

The study also reported significant cardiovascular effects. Heart rate varied by more than 21 beats per minute between fluvoxamine and nortriptyline, and blood pressure differences reached 11 mmHg between nortriptyline and doxepin.

Amitriptyline, for instance, was associated with an average weight gain of 1.5 kilograms, a 9 bpm increase in heart rate, and a 5 mmHg rise in blood pressure, indicating elevated cardiovascular risk.

Some drugs, including paroxetine, duloxetine, desvenlafaxine, and venlafaxine, were linked to slight weight loss but increased cholesterol and glucose levels.

Experts caution that even modest changes in weight, heart rate, or blood pressure can elevate long-term risks for heart disease, stroke, and metabolic disorders.

Serotonin–noradrenaline reuptake inhibitors (SNRIs) and tricyclic antidepressants showed more pronounced effects, while selective serotonin reuptake inhibitors (SSRIs) generally had milder impacts.

For example, sertraline was associated with slight weight loss and a small reduction in heart rate, whereas citalopram produced minor decreases in heart rate and systolic blood pressure.

Preexisting conditions

The researchers emphasise the importance of ongoing physical health monitoring for individuals taking antidepressants, particularly those with preexisting cardiovascular conditions, hypertension, or obesity.

They also highlight the value of shared decision-making, ensuring that patients are fully informed and involved in treatment choices that align with their preferences, goals, and health needs.

According to the WHO, an antidepressant is a type of medication used to treat mental health disorders, primarily depression, but also other conditions such as anxiety disorders, post-traumatic stress disorder (PTSD), obsessive-compulsive disorder (OCD), certain sleep disorders, chronic pain, and eating disorders.

Antidepressants work by modifying the levels or activity of neurotransmitters in the brain, such as serotonin, norepinephrine, and dopamine, which help regulate mood, behaviour, and emotional responses.

WHO guidance emphasises that antidepressants should be used under medical supervision and are typically prescribed to:

• People diagnosed with moderate to severe depression, particularly when symptoms significantly affect daily functioning, work, relationships, or overall quality of life.
• Individuals with anxiety disorders or PTSD, when psychological therapies alone are insufficient.
• Patients with chronic pain, sleep disorders, or certain eating disorders, and if antidepressants are clinically indicated.

WHO also notes that not everyone with mild depressive symptoms requires antidepressants; sometimes non-drug interventions, such as psychotherapy, lifestyle changes, and social support, are recommended first.

Antidepressants should always be monitored for effectiveness and side effects, and patients should be educated about potential risks and the importance of adherence to the prescribed treatment.

Antidepressants are prescription-only medications because their use requires careful medical supervision to ensure safety and effectiveness.

A doctor must first confirm that the patient's symptoms warrant medication, as not all cases of low mood, anxiety, or stress require antidepressants. The right type, dose, and treatment duration vary between individuals, and only a healthcare professional can tailor these factors appropriately.

Prescription control also allows for monitoring of potential side effects, which can include changes in weight, heart rate, blood pressure, sleep patterns, or mood.

Some antidepressants may interact with other medications or underlying health conditions, making unsupervised use risky. Additionally, stopping or changing doses abruptly can cause withdrawal symptoms or worsen mental health symptoms.

By keeping antidepressant prescription-only, healthcare systems ensure that patients receive proper guidance, minimise risks, and maximise the likelihood of safe and effective treatment. This controlled access protects both the patient's physical and mental well-being while supporting long-term recovery.