Mental Illnesses

Mental illnesses are not a weakness of personality or a lack of faith, but conditions with a diagnosis, criteria and treatment like any other disease. Each disorder differs from the others in its symptoms and course, so talking about them as a single block doesn’t help. In this guide you will find the disorders divided into groups, each with a separate page explaining it in detail, then a quick look at diagnosis, treatment and when to seek help.

What are mental illnesses?

A mental illness is a disturbance in thinking, feelings, perception or behavior that lasts long enough and causes clear distress or disrupts work, study and relationships. The dividing line between it and ordinary sadness or stress isn’t the presence of the feeling itself, but its intensity, duration and effect on your day.

In diagnosis, doctors rely on two internationally approved systems: the Diagnostic and Statistical Manual of Mental Disorders issued by the American Psychiatric Association, and the International Classification of Diseases issued by the World Health Organization. Both divide the disorders into related families, which is the division this guide follows.

People often ask about the difference between psychological illness and mental illness, and the answer is that medicine doesn’t separate them the way popular usage does. You will find the details in the article The difference between psychological and mental illness.

Types of mental illness: a guide to the disorders

Choose the group closest to what you are looking for. Each name leads you to a full page about the disorder: its symptoms, causes, diagnosis and treatment, with separate articles on each aspect.

Mood disorders

A persistent change in mood that goes beyond passing sadness or joy, and affects sleep, energy and thinking.

• Depression: sadness or loss of pleasure lasting two weeks or more with disruption of daily life.
• Bipolar disorder: episodes of mania or hypomania alternating with episodes of depression.
• Mood swings: when they are a temperament and when they point to a disorder that needs assessment.

Anxiety, fear and obsessions

Fear or tension that exceeds the size of the situation, or repeated thoughts that force themselves on the person.

• Anxiety: constant worry that is hard to control, with panic attacks and accompanying physical symptoms.
• Social phobia: intense fear of how others see and judge you.
• Phobia: a specific fear of a particular thing or situation that drives avoidance.
• Obsessive-compulsive disorder: intrusive thoughts and repeated actions to relieve the anxiety they cause.
• Disorders related to obsession: compulsive hoarding, body dysmorphic disorder and hair-pulling disorder.

Trauma, stress and dissociation

Disorders that start after a traumatic event or major stress, or appear as a detachment from oneself or from reality.

• Post-traumatic stress disorder: intrusive memories, avoidance and hypervigilance after a traumatic event.
• Adjustment disorder: a reaction to a crisis that goes beyond what is expected in its intensity or duration.
• Dissociative identity disorder and depersonalization disorder: when a person feels detached from themselves or from what is around them.

Psychosis and schizophrenia

Disorders in which a person loses part of their contact with reality, and which need early assessment because rapid intervention changes their course.

• Psychosis: hallucinations, delusions or disturbed thinking, and it may be a symptom of more than one cause.
• Schizophrenia: a chronic disorder that combines psychotic symptoms with a decline in motivation and communication.
• Hallucination: hearing or seeing what doesn’t exist, and its psychological, organic and drug-related causes.

Personality disorders

Fixed patterns of thinking and dealing with others that start early and cause repeated problems in relationships and work.

• Personality disorders: the general picture and how to distinguish between temperament and disorder.
• Borderline personality, narcissistic personality and dependent personality.
• Masochism: when it becomes a pathological tendency that needs treatment.

Developmental and childhood disorders

They usually start in childhood, and some may continue into adulthood if not discovered.

• Attention deficit hyperactivity disorder and autism.
• Selective mutism, oppositional defiant disorder, Tourette syndrome and attachment disorder.

Sleep and eating

• Insomnia: persistent difficulty falling or staying asleep despite having the opportunity.
• Eating disorders: anorexia nervosa, bulimia and binge eating.

When the body speaks the language of the mind

Real physical symptoms with a psychological factor behind them, which need a doctor who connects the two pictures.

• Psychosomatic disorders, conversion disorder and factitious disorder.

Impulse control disorders

• Intermittent explosive disorder and kleptomania: an impulse that is hard to resist despite knowing its consequences.

The most common mental illnesses in the world

The latest estimates from the World Health Organization indicate that nearly one in every seven people in the world, about 1.2 billion people, were living with a psychological disorder in 2023, and that anxiety and depressive disorders are by far the most widespread. This table summarizes the published figures for the best-known disorders:

Despite this prevalence, most of those affected don’t receive effective treatment according to the same organization, even though prevention and treatment options exist and have been tested. So the most important step isn’t knowing the number, but asking for an assessment when the signs appear.

Is what I feel a mental illness or passing distress?

Distress is a normal part of life, and it usually calms down when its cause goes away. It becomes an illness when the symptoms last for weeks and intensify until they disrupt your sleep, work or relationships. The symptoms themselves vary between feelings, thinking, behavior and the body, and we have explained them in detail, with their signs in children and the elderly, on the page The symptoms and signs of mental illness.

And if your question is about the signs themselves, in feelings, thinking, behavior and the body, the dedicated guide for them is The symptoms of mental illness and its causes, which includes the differences between ages and the emergency signs.

Why do mental illnesses happen?

There is no single cause for almost any psychological disorder. A genetic predisposition overlaps with changes in brain chemistry, childhood experiences, trauma, ongoing pressures and substance use. The weight of each factor differs from one disorder to another. The article The causes of mental illness explains these factors one by one, and the article Hereditary mental illnesses answers the question of whether they pass to children.

How are mental illnesses diagnosed?

Psychiatric diagnosis doesn’t rely on a blood test or a scan alone, but on a structured medical interview in which the doctor asks about the symptoms, their onset and development, and about the medical and family history and the use of medicines or substances. They may use approved scales that help estimate severity.

The doctor sometimes asks for physical examinations or tests, not to diagnose the disorder itself, but to rule out organic causes that mimic the symptoms, such as thyroid disorders or the effects of some medicines. An accurate diagnosis sometimes needs more than one session, especially when the symptoms overlap between more than one disorder.

If you are hesitant about the first step, the article When do you need a psychiatrist explains the signs that call for a visit and what happens during it.

Treating mental illnesses: what options are available?

Treatment rests on two pillars used alone or together depending on the disorder and its severity:

• Psychotherapy: structured sessions such as cognitive behavioral therapy, exposure therapy and dialectical behavior therapy. You will find its types and how its sessions go in the section Psychotherapy.
• Medication: such as antidepressants, antipsychotics and mood stabilizers; the doctor determines their type, dose and duration and follows their effects. Don’t start or stop a psychiatric medicine without medical supervision.

Some cases need a period of residency in hospital, such as acute psychotic episodes or severe depression with a risk to the self, or when the disorder is accompanied by an addiction that needs detox under medical supervision.

Mental illnesses and addiction: dual diagnosis

A psychological disorder and addiction come together in many patients. Use may start as an attempt to calm anxiety or depression, and the substance may reveal a latent disorder or make it worse. Treating one without the other leaves the door open to relapse, which is why the Riviera Life team assesses the two conditions together and sets one plan for them.

The most serious mental illnesses: how is severity measured?

No disorder is “more serious” than the others in absolute terms. Severity is measured by three questions: is there a danger to the life of the person or others? Have they lost contact with reality? And to what extent has their ability to care for themselves been disrupted? That is why depression accompanied by suicidal thoughts may be more serious at that moment than a disorder that seems more severe on paper.

General signs shared by many mental illnesses

Each psychological disorder has its own picture, but there are general signs that appear in many of them, and they deserve attention if they last for weeks or affect work, study and relationships:

• A clear change in sleep: persistent insomnia or sleeping much more than usual.
• A change in appetite or weight without a known physical cause.
• Sadness, anxiety or irritability that lasts most of the day and doesn’t improve with time.
• Withdrawal from people and from activities that used to be enjoyable.
• Difficulty concentrating, making decisions or completing usual tasks.
• Repeated thoughts or fears that are hard to stop, or behaviors the person feels compelled to repeat.
• The feeling that reality has changed, hearing voices, or suspecting others without evidence.
• Turning to alcohol, drugs or sedative medicines to deal with feelings.

The presence of one sign doesn’t mean a mental illness, since we all go through difficult days. The deciding factor is persistence, intensity and the effect on daily life. That is why diagnosis always starts with an assessment carried out by a psychiatrist, not with a list on the internet.

Mental illnesses in children, teenagers and the elderly

The picture of mental illness differs with age. A child may not say they are sad or anxious, but shows it in tantrums, repeated stomach aches and headaches, refusing school, or a decline in studies. Among the most common at this stage are attention deficit hyperactivity disorder and anxiety disorders. A teenager’s depression, however, may appear as irritability, isolation and staying up late, and eating disorders and experimenting with drugs may begin at this age. In the elderly, depression may be mixed up with weak memory, so it is thought to be normal aging, while it is treatable. The details are in the articles Mental illness in children, Teen depression and Mental illness in the elderly.

When should you seek help?

Seek a specialist assessment if the symptoms last more than two weeks, or affect your work, study and relationships, or those around you notice a clear change in your behavior.

But if suicidal thoughts or self-harm appear, or hallucinations with dangerous behavior, or a complete cutting off from food and sleep, this is an emergency: call the ambulance on 123, or the mental health hotline 16328. The article Suicidal thoughts explains how to protect yourself and those you love.

And to protect your mental health on ordinary days, before pressures turn into a disorder, follow the mental health articles on stress, relationships and psychological resilience.