Understanding Mental Health Disorders: Types, Symptoms, and Support

Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026

A mental health disorder, also called a mental illness or psychiatric disorder, is a condition that affects how you think and behave, and it also influences your emotions and how you regulate them. These conditions are common: about 1 in every 8 people around the world lives with one, and there are more than 200 types [1].

Quick Answer: What is a mental health disorder?

A mental health disorder is a condition that affects your thoughts, emotions and behavior and can impact your ability to function at home, work or school. Common groups include anxiety, mood, eating, psychotic and substance use disorders. Diagnosis rests on an exam, history and psychological evaluation, and treatment may include psychotherapy and medications. These disorders are not character flaws. [1]

What the research says

• Mental disorders often begin early in life. A meta-analysis of 192 epidemiological studies (708,561 people) found that among people with a mental disorder, 34.6% had onset before age 14, 48.4% before age 18 and 62.5% before age 25, with a peak age at onset of 14.5 years. Neurodevelopmental disorders began earliest (61.5% before age 14), while only 11.5% of mood disorders began before age 18 (Solmi et al., Mol Psychiatry, 2022 [2]).

• When depression has not responded to at least two antidepressants, several other options beat placebo or sham treatment. A network meta-analysis of 69 randomized trials (10,285 participants) found that six of 25 treatments had higher response rates than placebo or sham: electroconvulsive therapy (ECT), minocycline, theta-burst stimulation, repetitive transcranial magnetic stimulation (rTMS), ketamine and aripiprazole. Odds ratios ranged from 1.9 (95% CI 1.25 to 2.91) for aripiprazole to 12.86 (95% CI 4.07 to 40.63) for ECT, and most studies (59.38%) had some risk-of-bias concerns (Saelens et al., Neuropsychopharmacology, 2025 [3]).

• In schizophrenia, real-world results can differ from trial results. A network meta-analysis combining 90,469 people from Swedish and Finnish registries with 10,091 participants from 30 randomized trials found that antipsychotic efficacy versus placebo in trials was larger than effectiveness versus no antipsychotic in real-world care (hazard ratio ratio 2.58; 95% CI 2.02 to 3.30). In the real-world analysis of relapse within six months, clozapine was most effective, followed by long-acting injectable olanzapine (Efthimiou et al., Lancet Psychiatry, 2024 [4]).

What Is a Mental Health Disorder?

A mental health disorder is a condition that affects the way you think and behave. You may feel anxious or empty, have racing thoughts, or have trouble eating or sleeping. There are several different types, and they may affect your ability to function at home, work or school [1].

What are the common types of mental health disorders?

Mental health disorders include more than 200 types, which fall into several broad categories. Some of the most common groups are [1]:

Category	Examples
Anxiety disorders	Post-traumatic stress disorder (PTSD), obsessive-compulsive disorder (OCD), social phobia and generalized anxiety disorder.
Mood disorders	Depression and bipolar disorder (manic depression).
Neurodevelopmental disorders	ADHD and autism.
Disruptive behavior disorders	Oppositional defiant disorder and conduct disorder.
Eating disorders	Anorexia nervosa, bulimia nervosa and binge eating disorder.
Personality disorders	Borderline, antisocial and narcissistic personality disorder.
Psychotic disorders	Schizophrenia.
Substance use disorders	Substance use disorder, addiction and alcohol use disorder.

Mental health disorders fall into several broad categories.

What are the symptoms and signs of mental health disorders?

Mental health conditions can lead to a broad range of symptoms that vary by type. A person does not have to have all of them to receive a diagnosis, but experiencing a few may be a sign to talk to a healthcare provider [1].

Symptoms in adults

• Behavior that seems out of character

• Changes in appetite, sex drive or daily functioning

• Difficulty identifying reality (hallucinations or delusions)

• Excessive worry, fear or unusual thoughts

• Feeling disconnected from yourself or others

• Heightened sensitivity to light, sound or smell

• Loss of interest in usual activities

• Mood swings or exaggerated emotions

• Performance issues at work or school, or relationship challenges

• Self-harm or thoughts of suicide

• Trouble sleeping

Symptoms in children

Mental disorders in children may affect how they think, feel and behave. You might notice that your child has [1]:

• Difficulty sitting still or paying attention

• Excessive worry or fear, such as not wanting to go to bed, or nightmares

• Decreased interest in favorite activities

• Frequent tantrums, defiance or aggressive behavior

• Problems at school or with friends

Symptoms can look different in adults and children.

What causes mental health disorders and who is at risk?

Many factors may contribute to the development of a psychiatric disorder [1]:

• Genetics: you may inherit genes that increase your risk of certain mental health conditions, but having these genes does not guarantee you will develop the disorder.

• Brain chemistry and function: your brain uses chemicals called neurotransmitters to help control mood and behavior, and disruptions in how these chemicals work may lead to mental disorders.

• Life experiences and environment: stressful experiences, especially early in life, may increase your risk, and so can substance use, the availability of social support and chronic medical conditions.

Anyone can develop a mental disorder, but your risk increases if you [1]:

• Experienced abuse or trauma

• Experienced significant stress, such as the loss of a loved one

• Feel isolated or lonely

• Had a traumatic brain injury

• Were exposed to viruses, toxic chemicals or substances (such as alcohol) before birth

• Have a biological family history of the condition

• Have a chemical imbalance in your brain

• Have a chronic or serious medical condition, such as chronic pain or cancer

• Use addictive substances

Mental health disorders can prevent you from feeling like yourself and may lead to thoughts of hurting yourself or others, including thoughts of suicide. If these thoughts are flooding your mind, do not hesitate to reach out for help. In the U.S., you can call or text 988 to reach the Suicide & Crisis Lifeline, where someone is available to talk 24/7, and you do not have to be in a crisis to call. If you are elsewhere, contact your local emergency services number [1].

How are mental health disorders diagnosed?

To diagnose a mental health condition, your provider will start with a physical exam and a review of your medical history, followed by a psychological evaluation in which a psychologist asks about your thoughts, feelings and behaviors. It helps to tell your provider about any specific triggers that make your symptoms worse, whether your symptoms are ongoing or come and go, and when you first noticed changes in your mental health [1].

There are no medical tests that can diagnose a mental disorder, but your provider may order blood work or imaging tests to rule out other conditions that can cause similar symptoms. A good first step is talking with a primary care physician, who may refer you to a psychologist or psychiatrist depending on your needs, and in some cases a social worker can help. After a diagnosis, a mental health therapist or counselor is often the person you see most regularly during therapy [1].

Being open and honest can feel vulnerable, which is normal, but your provider will not judge you, and your honesty helps them make an accurate diagnosis and offer the best care [1].

How are mental health disorders treated and supported?

Treatments for mental disorders may include [1]:

• Psychotherapy: talking to a mental health professional can help you better understand and manage your thoughts and behaviors, in an individual or group setting.

• Medications: psychiatric medications such as antidepressants, antipsychotics or mood stabilizers may help balance brain chemicals to ease symptoms.

• Supportive services: programs that offer education, social support and care coordination can help you manage your condition and adapt as your needs change.

• Alternate therapies: yoga, meditation or acupuncture may offer additional support alongside your regular treatment plan.

• Brain stimulation: for some disorders, therapies such as electroconvulsive therapy (ECT), vagus nerve stimulation (VNS) and transcranial magnetic stimulation (TMS) may help when other treatments are not effective.

If you are in crisis or your safety is at risk, you may need care in a hospital or outpatient treatment center, and your care team may coordinate follow-up treatment after you leave [1].

The care pathway runs from a primary care visit through evaluation and diagnosis to treatment and crisis support.

What is the outlook for mental disorders, and when to see a provider?

Treatment may help you feel better and make it easier to get through your day. It often takes time, and you may not feel better right away, but progress is possible. Some conditions improve over time, while others require long-term management, and your care team will work with you on a personalized plan based on your goals [1].

See a healthcare provider if symptoms are making it hard to get through your day, and let them know if you notice changes in the symptoms you experience. If you are in a crisis or need immediate help, contact 911 or your local emergency services number [1].

What is the bottom line on mental health disorders?

Mental health conditions are common and nothing to be ashamed of. They are not character flaws or signs of weakness, they can have many causes, and they are often more complex than they seem. A healthcare provider can help you understand what is going on and create a treatment plan that fits your life, and with the right care and support you can take meaningful steps toward feeling better and staying well [1].

Frequently Asked Questions

What is a mental disorder?

A mental disorder, also called a mental illness or psychiatric disorder, is a condition that affects how you think, feel and behave, and how you regulate your emotions. It can affect your ability to function at home, work or school [1].

How common are mental health conditions?

About 1 in every 8 people around the world lives with a mental disorder, which makes them very common [1].

What are the most common types of mental disorders?

Common types include anxiety disorders, mood disorders such as depression and bipolar disorder, neurodevelopmental disorders such as ADHD and autism, eating disorders, personality disorders, psychotic disorders such as schizophrenia, and substance use disorders [1].

What causes mental health disorders?

Many factors may contribute, including genetics, brain chemistry and function, and life experiences and environment, such as stress or trauma, especially early in life [1].

Can children have mental health disorders?

Yes. In children, signs can include difficulty sitting still or paying attention, excessive worry or fear, decreased interest in favorite activities, frequent tantrums or defiance, and problems at school or with friends [1].

What are the signs of a mental health problem in adults?

Signs include out-of-character behavior, mood swings or exaggerated emotions, changes in appetite or sleep, excessive worry or fear, loss of interest in usual activities, and feeling disconnected from yourself or others [1].

How is a mental disorder diagnosed?

There is no medical test that diagnoses a mental disorder. Your provider will do a physical exam, review your medical history and carry out a psychological evaluation, and may order blood work or imaging to rule out other conditions [1].

Who can diagnose a mental health condition?

A good first step is a primary care physician, who may refer you to a psychologist or psychiatrist. In some cases a social worker can help, and a therapist or counselor is often the person you see most during therapy after a diagnosis [1].

What treatments are available for mental disorders?

Treatments include psychotherapy, medications, supportive services, alternate therapies such as yoga or meditation, and brain stimulation for some disorders when other treatments are not effective [1].

Is there immediate help available for a mental health crisis?

Yes. In the U.S., you can call or text 988 at any time to reach the Suicide & Crisis Lifeline, which is available 24/7. If you are in a crisis or need immediate help, you can also contact 911 or your local emergency services number [1].

References

1. Cleveland Clinic. Mental Disorders. Cleveland Clinic. June 3, 2025. https://my.clevelandclinic.org/health/diseases/22295-mental-health-disorders

2. Solmi M, Radua J, Olivola M, et al. Age at onset of mental disorders worldwide: large-scale meta-analysis of 192 epidemiological studies. Mol Psychiatry. 2022;27(1):281-295. PMID 34079068. https://doi.org/10.1038/s41380-021-01161-7

3. Saelens J, Gramser A, Watzal V, et al. Relative effectiveness of antidepressant treatments in treatment-resistant depression: a systematic review and network meta-analysis of randomized controlled trials. Neuropsychopharmacology. 2025;50(6):913-919. PMID 39739012. https://doi.org/10.1038/s41386-024-02044-5

4. Efthimiou O, Taipale H, Radua J, et al. Efficacy and effectiveness of antipsychotics in schizophrenia: network meta-analyses combining evidence from randomised controlled trials and real-world data. Lancet Psychiatry. 2024;11(2):102-111. PMID 38215784. https://doi.org/10.1016/S2215-0366(23)00366-8

Medical disclaimer

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. The clinical information in this guide reflects source material last reviewed in June 2025.