The 5 most common mental illnesses worldwide

According to the World Health Organization, mental disorders are understood as “a combination of abnormal thoughts, perceptions, emotions, behaviour and relationships with others.” Mental illnesses are one of the most prominent afflictions on health worldwide; more than 971 million people suffer from them. 

But despite this, they can be highly stigmatized and misunderstood – impacting both patients’ access to care and quality of care. Of course this can cause a lot of worry and doubt in people with worries about their own mental health and the health of their family members.

Most people will experience a diagnosable mental health disorder, even if it may be short-lived.
Mental illnesses make up 16% of the global burden of disease globally (by Sydney Sims on Unsplash)

In this article, we’ll take a look at the most common mental illnesses around the globe – and later zoom in on the prevalence of mental disorders at home in the US. Let’s delve in:

Mental health statistics

  • Most people will experience a diagnosable mental disorder, even if it may be short-lived. This means people are more likely to experience a mental illness than diabetes, heart disease or cancer. 
  • That said, some of the most common mental disorders can also lead to major physical health problems. For example,  middle-aged and older adults with depression have been found more likely to have a stroke.
  • In teengers, mental health disorders make up 16% of the global burden of disease globally. Fifty percent of mental health conditions begin by age 14, yet many are not detected. In people aged 15-19, suicide is the third leading cause of death.
  • Around the world, there is a median of 9 mental health care workers per 100,000 population. 
  • Between 2010 and 2030, mental disorders could cost $16 trillion globally if more resources aren’t invested into mental health. 

What are some of the most common mental illnesses worldwide?

The Diagnostic and Statistical Manual of Mental Disorders (DSM–5) is used by health professionals globally to classify mental disorders. It lists dozens of mental disorders and classifies them in 20 categories. These include Neurodevelopmental Disorders, Schizophrenia Spectrum and Other Psychotic Disorders, Anxiety Disorders, and Depressive Disorders, for example. 

The Institute of Health Metrics and Evaluation’s (IHME) Global Burden of Disease Study 2017 zooms in on several of the most common mental illness worldwide and lists them by prevalence. Now, let’s take a look at a few: 

Most common mental illnesses in the world
More than 284 million people suffer from anxiety disorders (by Inzmam Khan from Pexels)

Anxiety disorders 

According to the IHME report, more than 284 million people suffer from anxiety disorders, making it one of the most common mental health disorders globally. According to the American Psychological Association (APA), anxiety is “an emotion characterized by feelings of tension, worried thoughts, and physical changes.”

That said, there are a range of different anxiety disorders – including generalized anxiety disorder, phobia, panic disorder, separation anxiety, obsessive compulsive disorder, social anxiety and post traumatic stress disorder.  While not every anxiety disorder brings the same symptoms, anxiety can cause things like dizziness, sweating, shaking, fatigue and hypertension, just to name a few. 

Depressive disorders

Depression negatively affects how people act and feel. It can cause patients to lose interest in activities they once enjoyed, feel hopeless or fatigued. It can also disrupt their sleep and appetite, or cause suicidal thoughts. It’s also another one of the most common mental illnesses: 264 million people are said to suffer from depressive disorders worldwide. 

There are various types of depression. One is Persistent Depressive Disorder, which is a more mild form of depression. Others include Postpartum Depression, which mothers may experience after giving birth. There’s also Seasonal Affective Disorder, which occurs during winter season and Psychotic Depression, which can lead to hallucinations. Bipolar disorder is defined by intense mood changes, is also considered a depressive disorder. 

As with many of the most common mental health disorders, people who suffer from depression are also more likely to suffer from some other mental  health disorders. These include generalized anxiety disorder, obsessive compulsive disorder or personality disorders. 

Attention-deficit hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is commonly known for affecting children – 8.4 percent of US school children have it. But ADHD is also prevalent in adults, and more than 73 million people have been diagnosed with ADHD worldwide. Symptoms include hyperactivity, trouble focusing, being impulsive, and having difficulty coping with stress. 

However symptoms can be subtle. Many adults might not realize they have ADHD (and that it has likely affected them since childhood).

Bipolar disorder

Another one of the most common mental illnesses is bipolar disorder. More than 45 million people worldwide are affected by it. 

Bipolar disorder brings on intense mood changes, and those with it may go from feeling happy and elated, to experiencing a depressive episode – in which they feel anxious or hopeless. People with bipolar disorder might also have mixed episodes. When this occurs, they experience both manic and depressive states. 

There’s four types of bipolar disorders, all which range in severity. For example Bipolar I Disorder is characterized by week-long manic episodes, or manic episodes in which the person needs to be hospitalized. Bipolar II Disorder is defined by depressive episodes, but not full manic or mixed ones. 

Cyclothymic Disorder is less severe, and includes consistent hypomania and depression lasting 2 years (but which are not intense enough to be considered episodes). There’s also something called Bipolar Not Otherwise Specified: a person has symptoms of bipolar disorder, but the symptoms don’t fit into the categories above.  

Conduct disorder 

Conduct disorder is seen in children and teens, and those with it tend to repeatedly disregard rules or other people’s safety. Symptoms include being aggressive toward people or animals, destroying property, or being unable to show signs of guilt. About 53 million people suffer from this condition. This makes it another one of the most common mental health illness

Most common mental illness in the US

So what does mental illness look like in the US? What are the most common mental disorders here at home? How many people suffer from mental illness, and how many receive treatment? 

According to the National Alliance on Mental Illness (NAMI) one in five adults in the US experience mental illness. And one in 25 adults face a serious mental illness. At the same time, 19 percent of US adults are affected by anxiety disorders. It also reports that 7 percent experience depression, 4 percent experience Post-traumatic Stress Disorder and another 3 percent are affected by bipolar disorder

Shockingly, in 2018, less than half of US adults with mental illness got treatment. Still, 8.4 million people acted as caregivers for someone with a mental disorder. These caregivers spent an average of 32 unpaid hours doing so.

Many of the most common mental illnesses are treatable, and those diagnosed with them can lead normal lives. Still, we must continue toward removing the stigma surrounding mental illness. After all, nearly 1 billion people globally are diagnosed with them.

– WHO (2019). Mental Disorders. Retrieved from
Reuben, A and Schaefer, J (2017). Mental Illness Is Far More Common Than We Knew. Retrieved from

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