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Understanding Mental Illness

This is an informational page created to help individuals, families, and communities better understand mental illness, common conditions, symptoms, diagnosis, treatment, recovery, support, stigma, and the importance of seeking help when it is needed.

This information is intended for education and awareness and should not replace an individualized evaluation, diagnosis, treatment plan, crisis response, or guidance from a qualified mental-health or healthcare professional.

Understanding Mental Illness

What Is Mental Illness? A Health Condition That Can Affect Thoughts, Emotions, Behavior, and Daily Life

Mental illness is a broad term used to describe mental, behavioral, or emotional health conditions that can significantly affect how a person thinks, feels, responds, relates to others, or functions in everyday life.

Mental illnesses are real health conditions. They are not personality flaws, moral failures, attention-seeking behaviors, or evidence that someone is weak.

A Health Condition

Mental Illness Can Affect Different Areas of a Person’s Life

A mental illness may affect emotions, thoughts, perceptions, behavior, motivation, concentration, sleep, energy, relationships, communication, self-care, work, school, or other daily responsibilities.

Some conditions may involve ongoing symptoms, while others may occur in episodes or become more noticeable during periods of stress, change, grief, trauma, illness, or reduced support.

The experience can vary significantly from one person to another. Two people with the same diagnosis may have different symptoms, strengths, needs, triggers, and responses to treatment.

A diagnosis can help describe a health condition, but it does not describe everything about the person living with it.

Thoughts

Changes in Thinking

A person may experience persistent worry, hopelessness, racing thoughts, intrusive thoughts, difficulty concentrating, confusion, unusual beliefs, or changes in how they interpret experiences.

Emotions

Changes in Mood or Regulation

Emotions may feel unusually intense, absent, difficult to regulate, or disconnected from what is happening. A person may experience sadness, fear, irritability, emotional numbness, elevated mood, or rapid changes in mood.

Behavior

Changes in Actions or Habits

Mental illness may affect sleep, eating, activity, personal care, communication, substance use, risk-taking, avoidance, social interaction, or the ability to complete normal responsibilities.

Functioning

Difficulty Managing Daily Life

Symptoms may interfere with relationships, education, employment, parenting, decision-making, finances, healthcare, home responsibilities, independence, or personal safety.

Different Types of Conditions

Mental Illness Is Not One Single Experience

The term mental illness includes many different conditions. Each condition has its own diagnostic criteria, possible symptoms, course, and treatment considerations.

Anxiety Disorders

Conditions involving excessive fear, anxiety, worry, avoidance, panic, or physical stress responses.

Depressive Disorders

Conditions that may involve persistent sadness, hopelessness, reduced interest, low energy, or changes in sleep, appetite, and functioning.

Bipolar and Related Disorders

Conditions involving significant episodes or shifts in mood, energy, activity, sleep, judgment, and functioning.

Trauma-Related Conditions

Conditions that may develop after traumatic or deeply distressing experiences and affect safety, memory, emotions, sleep, and stress responses.

Obsessive-Compulsive Disorder

A condition involving unwanted intrusive thoughts, urges, or images and repetitive behaviors or mental acts.

Eating Disorders

Serious conditions involving eating behavior, body image, thoughts, emotions, physical health, and relationships with food.

Psychotic Disorders

Conditions that may affect perception, beliefs, thinking, communication, emotional expression, or a person’s experience of reality.

Personality Disorders

Conditions involving long-term patterns of inner experience, emotional regulation, behavior, identity, or relationships that cause distress or impairment.

No Single Explanation

Mental Illness Can Develop Through Multiple Influences

Mental illness is rarely explained by one single event, personal choice, or biological factor. Different influences may interact across a person’s life.

Biological Influences

Genetics, brain development, physical health, hormones, sleep, medication, substance use, injury, and other biological factors may affect vulnerability or symptoms.

Psychological Influences

Coping patterns, emotional regulation, beliefs, previous experiences, trauma, grief, stress, and learned responses may affect mental well-being.

Social Influences

Relationships, isolation, financial insecurity, housing, discrimination, violence, work, school, community, culture, and access to care can influence mental health.

Recovery and Support

Mental Illness Can Be Treated and Supported

Support may include therapy, medication, peer support, community services, accommodations, physical healthcare, crisis planning, supportive relationships, lifestyle changes, or a combination of approaches.

The most appropriate care depends on the condition, severity, symptoms, safety needs, health history, culture, preferences, resources, and individual circumstances.

Recovery does not always mean that every symptom disappears. It may mean gaining greater stability, understanding symptoms, developing effective support, improving functioning, building meaningful relationships, or creating a fulfilling life.

A person may live with a mental illness, but mental illness is not the totality of who they are.

Understanding Different Conditions

There Are Many Types of Mental Illness Here Are Some Commonly Discussed Conditions

Mental illness is not one single experience. There are many different conditions that may affect thoughts, emotions, perception, behavior, relationships, physical health, or daily functioning.

Some conditions share similar symptoms, but they are not interchangeable. The reason a symptom occurs, how long it lasts, when it began, and how it affects the person’s life are all important when determining an appropriate diagnosis and support plan.

Before Exploring the Conditions

A Symptom Is Not Automatically a Diagnosis

Many people occasionally experience sadness, worry, irritability, intrusive thoughts, changes in sleep, difficulty concentrating, or emotional distress. Having one of these experiences does not automatically mean that someone has a mental illness.

A professional evaluation considers the complete pattern, including the severity and duration of symptoms, developmental and medical history, life experiences, safety, substance use, medications, physical health, and the degree to which symptoms interfere with everyday functioning.

Two people may have similar outward symptoms for very different reasons, and two people with the same diagnosis may experience it very differently.

01

Anxiety Disorders

More Than Occasional Worry

Anxiety is a normal human emotion, but an anxiety disorder may be present when fear, worry, physical tension, or avoidance becomes persistent, difficult to control, and disruptive to daily life.

What It May Feel Like

  • Constant worry that feels difficult to stop
  • A sense that something bad is about to happen
  • Racing thoughts or repeated “what if” questions
  • Fear of embarrassment, judgment, danger, or losing control
  • Difficulty relaxing even when the person is safe

How It May Affect the Body

  • Rapid heartbeat or chest discomfort
  • Shortness of breath or dizziness
  • Muscle tension, shaking, or sweating
  • Stomach discomfort or nausea
  • Sleep difficulties and physical exhaustion

Anxiety disorders include several conditions, such as generalized anxiety disorder, panic disorder, social anxiety disorder, separation anxiety disorder, and specific phobias.

02

Depressive Disorders

More Than Having a Difficult Day

Depression may involve a persistent depressed, empty, or irritable mood, a loss of interest or pleasure, and other changes that interfere with a person’s ability to function.

Emotional and Cognitive Signs

  • Persistent sadness, emptiness, or irritability
  • Hopelessness or a belief that nothing will improve
  • Loss of interest in previously meaningful activities
  • Excessive guilt, shame, or feelings of worthlessness
  • Difficulty concentrating or making decisions

Physical and Daily-Life Signs

  • Low energy or feeling physically slowed down
  • Sleeping much more or much less than usual
  • Changes in appetite or weight
  • Withdrawing from relationships and responsibilities
  • Difficulty completing basic care or daily tasks

Depression is different from ordinary sadness or temporary disappointment. It can affect the entire body and may become severe enough to involve thoughts of death or suicide.

03

Bipolar and Related Disorders

Significant Episodes of Mood and Energy Change

Bipolar disorder involves distinct episodes that cause significant changes in mood, energy, activity, sleep, concentration, judgment, and functioning. It is not the same as ordinary moodiness or rapidly changing emotions during one difficult day.

Manic or Hypomanic Symptoms

  • Unusually elevated, energized, or irritable mood
  • Decreased need for sleep without feeling tired
  • Rapid speech, racing thoughts, or many new ideas
  • Increased confidence or an inflated sense of ability
  • Impulsive, risky, or uncharacteristic decisions

Depressive Symptoms

  • Deep sadness, emptiness, or hopelessness
  • Loss of interest or pleasure
  • Low energy and difficulty completing tasks
  • Changes in sleep, appetite, or concentration
  • Thoughts about death, self-harm, or suicide

Bipolar I disorder, bipolar II disorder, and other related conditions are not identical. The type, duration, severity, and pattern of mood episodes matter when making a diagnosis.

04

Post-Traumatic Stress Disorder

When the Effects of Trauma Continue

People can experience many reactions after trauma, and not everyone who experiences trauma develops PTSD. PTSD may develop when trauma-related symptoms continue, cause significant distress, and interfere with everyday life.

Re-Experiencing and Avoidance

  • Intrusive memories, nightmares, or flashbacks
  • Strong physical or emotional reactions to reminders
  • Avoiding people, places, conversations, or activities
  • Avoiding thoughts or feelings connected to the trauma
  • Feeling as though the event is happening again

Ongoing Changes After Trauma

  • Feeling constantly alert, unsafe, or easily startled
  • Irritability, anger, or difficulty sleeping
  • Emotional numbness or disconnection
  • Guilt, shame, or negative beliefs about oneself
  • Difficulty trusting or connecting with other people

PTSD is not a sign that someone is weak or failed to “move on.” It reflects a continuing response to an experience that overwhelmed the person’s sense of safety or control.

05

Obsessive-Compulsive Disorder

More Than Being Organized or Particular

OCD may involve uncontrollable, recurring thoughts, images, or urges called obsessions and repetitive actions or mental acts called compulsions. These experiences may become time-consuming and cause significant distress.

Obsessions

  • Unwanted fears about harm, contamination, or mistakes
  • Disturbing intrusive thoughts or mental images
  • A need for certainty, symmetry, or things to feel correct
  • Persistent doubt about actions or memories
  • Thoughts that conflict with the person’s values

Compulsions

  • Repeated checking, cleaning, counting, or arranging
  • Repeating words, prayers, or phrases mentally
  • Seeking reassurance repeatedly
  • Avoiding situations that trigger an obsession
  • Performing rituals to reduce fear or prevent harm

People with OCD generally do not perform compulsions because they enjoy them. The behavior is often an attempt to reduce intense distress, doubt, fear, or a sense of incompleteness.

06

Eating Disorders

Serious Conditions That Affect the Mind and Body

Eating disorders involve serious disturbances in eating behavior and related thoughts or emotions. They can affect people of every body size, gender, race, culture, age, and background.

Possible Experiences

  • Restricting food or avoiding entire food categories
  • Episodes of eating unusually large amounts of food
  • Vomiting, fasting, or exercising to compensate for eating
  • Fear, shame, secrecy, or loss of control around food
  • Preoccupation with weight, shape, calories, or eating

Why Early Support Matters

  • Eating disorders can affect every organ system
  • Serious medical complications may occur at any weight
  • Symptoms may be hidden from family or professionals
  • Other mental-health conditions may occur alongside them
  • Early identification can improve recovery outcomes

Examples include anorexia nervosa, bulimia nervosa, binge-eating disorder, avoidant/restrictive food intake disorder, and other specified feeding or eating disorders.

07

Borderline Personality Disorder

Significant Difficulty Regulating Emotions and Relationships

Borderline personality disorder can severely affect a person’s ability to regulate emotions. It may also influence identity, relationships, behavior, self-image, and responses to rejection, separation, or perceived abandonment.

Emotional and Identity Experiences

  • Intense emotions that may change rapidly
  • Persistent emptiness or uncertainty about identity
  • Strong sensitivity to rejection or abandonment
  • Difficulty calming after emotional distress
  • Feeling disconnected, unreal, or emotionally overwhelmed

Relationship and Behavior Patterns

  • Relationships that may feel especially intense
  • Rapid changes in how another person is perceived
  • Impulsive actions during emotional distress
  • Anger that feels difficult to control
  • Self-harm or suicidal behavior in some individuals

Borderline personality disorder is frequently stigmatized and misunderstood. It is a treatable mental illness, and symptoms can improve significantly with appropriate care and support.

08

Schizophrenia

A Serious Condition Affecting Thought, Perception, and Functioning

Schizophrenia is a serious mental illness that can affect how a person thinks, feels, perceives experiences, communicates, and behaves. It does not mean that someone has multiple personalities.

Psychotic Symptoms

  • Hallucinations, such as hearing or seeing things
  • Delusions or firmly held beliefs not supported by evidence
  • Disorganized thinking or difficulty organizing speech
  • Behavior that appears highly confused or disorganized
  • Difficulty distinguishing some experiences from reality

Cognitive and Reduced-Function Symptoms

  • Difficulty with attention, memory, or decision-making
  • Reduced emotional expression
  • Reduced motivation or difficulty beginning activities
  • Withdrawal from relationships or daily responsibilities
  • Difficulty communicating or maintaining functioning

Psychosis can occur in schizophrenia, but it may also occur in other mental illnesses, medical conditions, substance-related conditions, or severe mood episodes. Psychosis is a symptom, not automatically a diagnosis of schizophrenia.

Conditions Can Overlap

More Than One Condition May Be Present

A person may meet the criteria for more than one mental-health condition. This is sometimes referred to as co-occurrence or comorbidity. One condition may also affect the presentation, severity, or treatment of another.

Anxiety and depression may occur together.

PTSD may occur alongside depression, anxiety, or substance-use concerns.

Eating disorders may occur alongside anxiety, depression, or OCD.

Autism or ADHD may coexist with one or more mental-health conditions.

Understanding the Whole Person

These Are Only Some of the Many Mental Illnesses

There are many additional mental-health conditions and diagnostic categories that are not included in this short overview. Some conditions also contain several subtypes or presentations.

Symptoms should be interpreted within the person’s full developmental, medical, psychological, social, and cultural context. A checklist alone cannot determine why someone is struggling.

Treatment and support may include psychotherapy, medication, peer support, medical care, accommodations, community services, crisis planning, family education, or a combination of approaches.

Learning about mental illness should increase understanding and access to support—not encourage assumptions, labels, fear, or judgment.

Understanding Vulnerability

Risk Factors for Mental Illness Risk Is Influenced by Biology, Experiences, Environment, and Support

A risk factor is something that may increase the likelihood of developing a mental-health condition. Risk factors can affect people differently and often interact rather than operating independently.

Having one or more risk factors does not mean that someone will develop a mental illness. A person may have several risk factors and never develop a condition, while another person may develop one without an obvious or identifiable cause.

An Important Distinction

Increased Risk Does Not Mean Inevitable Illness

Risk factors describe circumstances or characteristics that may increase vulnerability. They do not predict with certainty what will happen to one individual.

People differ in genetics, development, coping strategies, relationships, resources, culture, access to care, and the meaning they assign to their experiences.

Protective factors—such as safety, stable housing, supportive relationships, coping skills, accommodations, healthcare, community connection, and early intervention—may help reduce the impact of risk.

Risk factors should be used to understand where support may be needed—not to label, judge, blame, or predict someone’s future.

Biological and Genetic Factors

Physical and Developmental Vulnerability

Biology can influence how vulnerable a person may be to certain mental-health conditions. This does not mean that one gene, brain difference, or physical characteristic causes every mental illness.

  • A family history of certain mental-health conditions
  • Genetic vulnerability
  • Differences in brain development or functioning
  • Hormonal or neurological changes
  • Complications during pregnancy or birth
  • Brain injury or certain neurological conditions
  • Chronic illness, pain, or other physical-health concerns

Childhood and Developmental Experiences

Early Experiences Can Shape Stress and Safety

Childhood does not determine a person’s future, but repeated adversity during development may affect emotional regulation, relationships, self-perception, and responses to stress.

  • Abuse, neglect, or exploitation
  • Bullying, rejection, or social exclusion
  • Household violence or instability
  • Loss of a parent or caregiver
  • Inconsistent access to safety and basic needs
  • Separation from family or community
  • Growing up without appropriate disability support

Trauma and Chronic Stress

Experiences That Overwhelm the Ability to Cope

Trauma and prolonged stress may affect the nervous system, sense of safety, sleep, emotions, memory, relationships, and physical health. Not everyone who experiences trauma develops a mental illness.

  • Physical or sexual violence
  • Emotional abuse or coercive control
  • Serious accidents or medical trauma
  • War, displacement, or community violence
  • Repeated exposure to threatening situations
  • Sudden or traumatic bereavement
  • Long-term caregiving pressure or chronic stress

Social and Relationship Factors

Connection, Belonging, and Support Matter

Human beings are affected by the quality of their relationships and their ability to experience safety, belonging, dignity, and meaningful connection.

  • Social isolation or prolonged loneliness
  • Relationship conflict or family instability
  • Abandonment, rejection, or loss
  • Lack of trusted emotional support
  • Caregiver stress or family illness
  • Unhealthy or controlling relationships
  • Repeated experiences of being misunderstood or excluded

Environmental and Structural Factors

Mental Health Is Affected by Living Conditions

Mental health is not shaped only by individual choices. Economic, environmental, political, and social conditions can create ongoing stress and limit access to safety or support.

  • Poverty or financial instability
  • Housing insecurity or homelessness
  • Unsafe neighborhoods or community violence
  • Unemployment or harmful working conditions
  • Limited access to education or healthcare
  • Food insecurity or transportation barriers
  • Major disasters, displacement, or environmental instability

Discrimination and Inequality

Repeated Marginalization Can Affect Well-Being

Discrimination can create chronic stress, reduce safety, restrict opportunities, and make it harder to access respectful and culturally appropriate support.

  • Racism and racial discrimination
  • Ableism and disability-related exclusion
  • Sexism or gender-based violence
  • Homophobia or transphobia
  • Religious or cultural discrimination
  • Stigma related to mental illness
  • Institutional barriers and unequal treatment

Health, Sleep, and Substance-Related Factors

Physical Conditions Can Affect Mental Functioning

Sleep, substances, medication, physical illness, and other health factors may contribute to symptoms, worsen an existing condition, or create experiences that resemble mental illness.

  • Long-term sleep deprivation
  • Alcohol or drug use
  • Withdrawal from certain substances
  • Medication effects or interactions
  • Chronic pain or fatigue
  • Hormonal, metabolic, or neurological concerns
  • Limited access to consistent physical healthcare

Major Life Events and Transitions

Significant Change Can Increase Stress

Even positive changes can require major emotional, psychological, financial, or practical adjustment. Multiple transitions occurring together may increase vulnerability.

  • Death, grief, or separation
  • Divorce or the end of a relationship
  • Moving or losing stable housing
  • Job loss or career disruption
  • Pregnancy, childbirth, or becoming a caregiver
  • Receiving a serious health diagnosis
  • Entering or leaving school, work, or military service

Neurodevelopment and Mental Health

Neurodivergence Is Not Mental Illness, but Experiences Can Overlap

Autism and ADHD are neurodevelopmental conditions, not mental illnesses. However, autistic people and people with ADHD can also develop separate mental-health conditions.

Mental-health vulnerability may increase when a neurodivergent person experiences chronic sensory overload, masking, bullying, isolation, communication barriers, discrimination, inaccessible environments, or unmet support needs.

Symptoms may also be overlooked when distress is incorrectly dismissed as “just autism” or “just ADHD.” At the same time, neurodevelopmental traits should not automatically be mistaken for signs of mental illness.

Support should consider both the person’s neurodevelopmental needs and any separate mental-health symptoms they may be experiencing.

Protective Factors

Supportive Conditions Can Strengthen Mental Health

Protective factors do not make someone immune to mental illness, but they may improve coping, reduce exposure to harm, support recovery, and make it easier to seek help early.

Safe and stable housing

Supportive relationships and community connection

Access to respectful physical and mental healthcare

Healthy coping skills and emotional education

Financial, educational, and employment stability

Disability accommodations and accessible environments

Consistent sleep, physical care, and opportunities for rest

Early recognition and support when difficulties appear

Look at the Complete Picture

Mental Illness Is Rarely Caused by One Thing

Mental illnesses generally develop through a complex interaction of vulnerability, stress, development, relationships, physical health, life experiences, and environmental conditions.

Identifying a risk factor is not the same as blaming a person, parent, family, culture, or community. It is also not proof that one event caused the condition.

Understanding risk can help individuals, families, professionals, and communities recognize where prevention, accommodation, safety, treatment, or additional support may be needed.

Risk factors increase possibility—not certainty. Every person should be understood through their full history, current circumstances, individual strengths, and support needs.