Understanding Common Types of Mental Illness

types of mental illness

Everyone’s mental health dips from time to time. But it can be difficult to separate these universal struggles from the types of mental illness that need medical intervention.

This guide explores five common types of mental illness and their characteristics. It might help you identify signs in yourself and others that it’s time to consider professional help.

The Mental Health Continuum Model

Everyone’s mental state sits on a spectrum ranging from extremely healthy to severely unwell. No one’s position on this spectrum is fixed and people are rarely on the extreme ends.

Depending on the circumstances and support available, our mental state can move from positive to negative. Move far enough and there’s a point where poor mental health becomes diagnosed as an illness. This point usually comes when the symptoms are persistent and significantly interfere with daily life.

Seeking Support

Several of the mental illnesses discussed in this guide can start as poor mental health. If left unmanaged, these struggles can develop into diagnosable mental health conditions.

Treating these illnesses through a range of support strategies and clinical interventions is possible. But this guide explains how to recognise common types of mental illness. It doesn’t cover treatment options.

If you’re seeing signs of a serious mental health condition in yourself or someone else, it’s vital to seek professional help.

Speaking to your GP is always recommended. You can also find mental health services via the NHS website.

Common Types of Mental Illness


Anxiety is one of the most commonly diagnosed types of mental illness in the UK. The Mental Health Foundation (MHF) suggests almost 8% of British adults fit the criteria to be diagnosed with mixed anxiety and depression.

Everyone feels anxious from time to time. Distinguishing between this type of anxiety and the type that’s diagnosable as a mental health disorder comes down to its effects.

People living with anxiety disorders face extreme feelings of dread or worry. These feelings can be triggered by external forces, such as work stress, but are completely disproportional. They’ll also endure for extended periods, often lasting beyond the stressful situation that caused them.

There are many subtypes of anxiety disorders, including social anxiety, panic disorders and phobias. Severe anxiety often manifests as Generalised Anxiety Disorder (GAD). As the name suggests, this disorder causes intense worry over everyday issues and lacks specific triggers. GAD symptoms are similarly undefined and affect people differently but common signs include:

  • Difficulty concentrating
  • Difficulty sleeping
  • Physical and mental exhaustion
  • Increased irritability

Mental Health Awareness Training

Our Mental Health Awareness Training course develops an understanding of common mental health issues. It explores how and why people might suffer from poor mental health and the ways we can improve and protect our mental wellbeing.


Depression is the other most commonly diagnosed type of mental illness in the UK. The MHF reports that up to 10% of adults will experience depression in their lifetime.

Similar to anxiety, we all experience low moods occasionally. If these low moods persist and interfere with your daily life, it may be a sign of depression.

Common symptoms include:

  • Low self-esteem
  • Feelings of despair or hopelessness
  • Feeling isolated and unable to relate to others
  • Consistent feelings of exhaustion
  • Being quick to anger over minor setbacks
  • Losing interest in previously enjoyed activities
  • Struggling to sleep
  • Changing habits around food, either eating more or less than usual

People experiencing depression can turn to unhealthy coping strategies to manage these symptoms. Almost all will isolate themselves and neglect relationships. Self-medicating with alcohol or recreational drugs is also common. Extreme cases may drive some to display suicidal behaviours or self-harm.

If you recognise any of these signs, it’s essential you seek professional help.

Personality Disorders

Personality disorder is a collective term for a group of different conditions. They’re generally characterised by unhealthy patterns of thinking, feeling and behaving. A person with a personality disorder will struggle to interpret and relate to situations and people.

The common symptoms seen across each form of personality disorder include:

  • Experiencing sudden and dramatic mood swings
  • Avoiding social interactions and maintaining few close relationships
  • Engaging in compulsive and harmful behaviours without considering the consequences
  • Holding a distorted sense of self-identity and self-worth
  • Falling out with others due to misunderstandings or misinterpretations
  • Being suspicious about others’ motives
  • Feeling detached from reality or oneself (dissociation)
  • Attempting to Influence or control others for personal gain or dominance
  • Fearing abandonment

While personality disorders are less common than anxiety or depression, they have a high profile. The symptoms are harder to hide than those of other conditions. They also directly affect relationships, making it more likely that family and close friends will recognise something is wrong.

There is some controversy around the diagnosis of personality disorders. They’re relatively well-known because it’s easy for some to dismiss difficult people as having some form of personality disorder. This labelling is insensitive and increases the stigma around the condition.

Some people diagnosed with personality disorders also disagree with the label. They often feel their erratic behaviour is justified by their challenging life circumstances. In their view, the term ‘personality disorder’ ignores this context and suggests the symptoms come entirely from them as individuals.


Stress is one of the most common types of mental health issues. It’s not recognised as its own condition but is a common cause or result of more serious mental health problems.

While stress is a human response to everyday pressures, it can become harmful when excessive and poorly managed. Medical professionals typically categorise harmful stress as either acute or chronic.

Acute Stress

Most people experience acute stress. It’s usually a response to a specific event or situation. As acute stress is situational, it is typically short-term and often fades after the challenging situation has passed.

This type of stress can even be beneficial in small doses, motivating you or helping you to focus. However, when excessive, acute stress has several harmful physical and psychological effects.

Symptoms of acute stress include:

  • Feelings of irritability or anger
  • Feelings of depression or anxiety
  • Difficulty sleeping
  • Physical symptoms, including headaches, rapid heart rate or chest pain

Chronic Stress

Chronic stress occurs over an extended period. This type of stress wears on people day after day and can lead to significant health problems.

Chronic stress can be the result of ongoing poverty, dysfunctional families or prolonged job pressures. Symptoms overlap with those of acute stress and may include:

  • Persistent fatigue that doesn’t seem to get better with rest
  • Difficulty concentrating or being productive
  • Detrimental effects on existing health conditions, such as high blood pressure, heart disease or diabetes

Managing chronic stress requires substantial lifestyle adjustments and sometimes professional help to prevent significant health consequences.


Trauma, like stress, is not a specific mental health condition. It’s an emotional response to a deeply distressing or disturbing event.

Trauma is a personal experience; what may be traumatic for one person might not affect another the same way. However, certain events are widely recognised as traumatic. These events can include severe accidents, natural disasters and suffering violence or severe neglect.

Everyone responds to trauma differently depending on their personal background, resilience and available support systems. Reactions can vary from immediate shock and denial to longer-term responses such as unpredictable emotions, difficulty maintaining relationships and even physical symptoms like headaches or nausea.

Groups at Greater Risk of Trauma

Certain groups may be more vulnerable to trauma because of their increased exposure to stressful conditions. Trauma is more prevalent in:

  • People of colour
  • People who identify as LGBTQ+
  • People who are seeking asylum or fleeing conflict
  • People who have been in or are in prison
  • People who are serving or have served in the armed forces

Post-Traumatic Stress Disorder

If trauma is not properly addressed, it can develop into Post-Traumatic Stress Disorder (PTSD). A person with PTSD effectively re-lives their traumatic experience and the intense feelings it caused long after the event occurred.

Symptoms of PTSD include:

  • Persistent re-experiencing of the traumatic event (e.g., flashbacks, nightmares)
  • Avoidance of stimuli associated with the trauma (e.g., places, activities, people)
  • Heightened reactions (e.g., excessive emotions, mood swings, difficulty sleeping)

Maintaining Your Mental Health

Maintaining your mental health is critical to living a balanced and fulfilling life. Our mental state influences how we think, feel and behave. It also affects our ability to manage stress, build relationships and recover from life’s setbacks.

While different types of mental illness usually need treatment, lifestyle changes can help you cope with everyday challenges. There are a number of proven strategies you can use to maintain good mental health:

  • Stay Connected: Keep in touch with understanding friends and family. Relationships can provide essential emotional support and help you manage during tough times.
  • Be Physically Active: Regular physical activity can boost your mood and help reduce the symptoms of depression and anxiety.
  • Get Adequate Rest: Restorative sleep is essential for our overall health. A good night’s sleep boosts your mood, energy levels and emotional resilience.
  • Eat a Balanced Diet: Nutrition can affect your mental health. Balanced diets support brain function and overall wellbeing.
  • Seek Professional Help When Needed: If you feel overwhelmed or unable to cope, don’t hesitate to contact mental health professionals.
Maintaining Your Mental Health

Mental Health Awareness Training

One effective strategy to improve and maintain mental health is through awareness training. Mental Health Awareness Training equips individuals with the knowledge and skills to better understand, manage and support mental health—both their own and others’.

By demystifying mental health issues, awareness training plays a crucial role in combatting stigma and encouraging people suffering to open up. It also offers insights into common mental health problems, helping you recognise symptoms early and offer support before issues can escalate.

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Jonathan Goby
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