Where does a bad week end and a mental health problem begin?

What good mental health looks like

• Mental health is how we think, feel and cope. Everyone has it.
• Good mental health includes positive engagement with society and coping effectively with challenges.
• Everyone has bad days. A significant mental health problem is more severe, lasts longer and disrupts daily life.
• A clinician makes a diagnosis using ICD (the International Classification of Diseases).

How common, and is it rising?

• About 1 in 5 adults in England (20.2%) had a common mental health condition, such as depression or anxiety, in 2023/4 (NHS England 2025).
• Ages 16 to 64: up from 15.5% (1993) to 22.6% (2023/4).
• About 1 in 5 people aged 8 to 25 had a probable mental disorder (NHS England 2023).
• These show prevalence (cases at one time); incidence is new cases over a period.

Why recorded rates change

• Modern living brings extra challenges, eg isolation and loneliness.
• Recognition: people, schools and doctors now spot problems more often, so more cases are recorded.
• Less stigma: stigma means negative attitudes and stereotypes. As it lessens, more people ask for help and get diagnosed.
• Culture: beliefs differ about what counts as a problem, what causes it (spiritual or medical) and whether to seek help.

Effects on the person and on society

• Individual: damage to relationships, difficulty coping with day-to-day life (school, work, looking after yourself) and harm to physical wellbeing.
• Society: more need for social care and health services, and costs to the economy when people can't work.
• Some problems are linked with higher crime rates, but most people with mental health problems never commit a crime.

Everyone feels sad sometimes. When do doctors call it depression?

Sadness or depression?

• Sadness is a normal emotion, usually triggered by an event such as a loss. It lifts.
• Clinical depression is a mental health problem: persistent low mood with other symptoms that affect daily life, with or without an obvious trigger.
• Unipolar depression: mood moves one way only, down.
• Bipolar depression (bipolar disorder): periods of depression alternate with mania: high mood or irritability, high energy, racing thoughts, less need for sleep.

The ICD symptoms of depression

• Clinicians use ICD (the International Classification of Diseases), published by the World Health Organization (WHO).
• Key features: low mood (sad, empty or irritable) or loss of interest or pleasure in activities.
• Other symptoms include reduced energy, changes in sleep, changes in appetite or weight, decreased self-confidence or self-worth, excessive guilt, poor concentration and hopelessness about the future.

Number, severity and time

• Symptoms must be present most of the day, nearly every day, for at least two weeks.
• The clinician judges the number of symptoms, how severe they are and how much they affect daily life.
• Depression is then classed as mild, moderate or severe: more symptoms, and more severe ones, mean a more severe episode.
• A clinician makes the diagnosis after talking with the person, never from a checklist alone.

Why do the same hard times trigger depression in only some people?

Looking inside the body: nature

• A biological explanation says depression has a physical cause in the body, eg in brain chemistry, genes or our evolution.
• This is the nature side of the nature–nurture debate. Nature means inherited, biological influences; nurture means the environment and experience.
• Stressful life events, such as losing a job or a bereavement, make depression more likely. That is nurture.

Serotonin and the synapse

• Neurotransmitters are chemicals that carry signals across the synapse, the gap between two neurons.
• Serotonin is a neurotransmitter linked to mood, sleep and appetite.
• The biological explanation says depression is caused by an imbalance of neurotransmitters, especially too little serotonin activity in the brain.
• Evidence: drugs that increase serotonin activity reduce symptoms for many people.

Nature, nurture or both?

• Biological explanations show that nature matters, but they rarely explain depression on their own.
• The diathesis–stress idea: a vulnerability (diathesis), eg in a person's biology, plus stress from life events together trigger depression.
• This explains why the same hard times lead to depression in some people but not others.
• The psychological explanation adds the nurture side.

Same bad news, two people: one shrugs, one spirals. Why?

It's how you think about it

• Psychological (cognitive) explanations say depression comes from the way a person thinks about events, not from the events alone.
• Negative, distorted thinking leads to low mood, and low mood makes negative thoughts easier to believe.
• These thinking patterns are learned through experience, eg criticism or loss in childhood. That is the nurture side of the nature–nurture debate.

Negative schemas and the negative triad

• A schema is a mental framework of beliefs built from experience.
• Beck's cognitive theory: negative experiences in childhood, such as criticism, rejection or loss, create negative schemas ("I'm a failure").
• Later events switch these schemas on, producing automatic negative thoughts.
• The negative triad: negative views of the self ("I'm useless"), the world ("everyone's against me") and the future ("it'll never get better").

Negative attributions

• An attribution is how you explain why something happened.
• People with depression tend to explain bad events in a way that is:
• internal: "It's my fault", not the situation;
• stable: "It'll always be like this";
• global: "I'm bad at everything".
• If the cause is you, permanent and everywhere, nothing seems able to change, which leads to hopelessness.

Cognitive explanations and nurture

• In the nature–nurture debate, cognitive explanations are on the nurture side: negative thinking is learned from experience, so it can be unlearned.
• Evidence: people with depression show more negative thinking than people without depression.
• But thinking is not the whole story: biology (nature) may also play a part, and the two may interact.

Why do doctors often treat depression with pills and talking?

Antidepressants at the synapse

• A common type of antidepressant is the SSRI (selective serotonin reuptake inhibitor), eg fluoxetine.
• Normally the sending neuron takes serotonin back from the synapse: reuptake.
• SSRIs block reuptake, so serotonin stays in the synapse longer and keeps stimulating the receiving neuron's receptors.
• This changes how neurons communicate, and over several weeks can lift mood. A doctor prescribes and monitors them.

CBT: changing thoughts and behaviour

• Cognitive behavioural therapy (CBT) is a talking therapy based on the cognitive explanation.
• The therapist helps the client identify negative thoughts and challenge them: what is the evidence?
• The behavioural part: planning enjoyable or useful activities, and homework to test thoughts in real life.
• Usually a course of regular sessions; the client learns skills to use alone.

Reductionist or holistic?

• A reductionist treatment targets one level of explanation. Antidepressants reduce depression to brain chemistry.
• CBT works on thoughts and behaviour: broader, but still one part of the person.
• A holistic approach treats the whole person: biology, thinking, relationships and life situation together, eg combining medication, therapy and practical support.
• Reductionist treatments are easier to test; holistic ones may fit real lives better.

Why combine treatments?

• Psychological treatments come first; for moderate or severe depression they can be combined with antidepressants. Mild depression doesn't need medication (WHO 2026).
• Medication can lift mood and energy enough for a person to engage with therapy.
• Therapy teaches skills that may help prevent depression returning after medication stops.
• Together they treat both biology and thinking: a more holistic approach.

Same habit, same years: why can one person stop and another can't?

Misuse or addiction?

• Substance misuse (or abuse) is using a substance in a harmful way or not as intended, e.g. above recommended limits, or a medicine not as prescribed.
• Addiction (medical term: dependence) is when the person has lost control: a strong need drives them to keep using despite harm.
• Misuse can happen without addiction, but repeated misuse can lead to dependence.
• People can also become addicted to behaviours, such as gambling.

How a clinician diagnoses dependence

• Clinicians use the ICD (the International Classification of Diseases), which calls addiction dependence syndrome.
• Strong desire to use the substance, despite harmful consequences.
• Difficulty controlling use: starting, stopping or how much.
• Higher priority for the substance than for other activities and obligations.
• Physical signs can include tolerance (needing more for the same effect) and withdrawal (feeling ill on stopping).
• Several features persist over months; a clinician makes the diagnosis.

Can addiction run in families?

• The biological explanation (influence of nature): some people inherit genetic vulnerability, genes that raise the risk of addiction.
• Genes may affect how strongly the brain's reward system responds, or how the body breaks a substance down.
• Twin studies compare identical (MZ) twins, who share 100% of their genes, with non-identical (DZ) twins, who share about 50%.
• Higher concordance (both twins affected) in MZ twins suggests genes play a part.

If friends and rewards build an addiction, can learning undo it?

Learning it from friends

• The psychological explanation (influence of nurture) says addiction is learned from the people around us.
• Peer influence: young people often start because their friends do. They observe and imitate peers they identify with.
• Seeing friends gain fun or status is vicarious reinforcement.
• Joining in brings acceptance; refusing risks rejection. The behaviour starts to seem normal.

Rewards that keep it going

• Operant conditioning: behaviour that is rewarded is repeated.
• Positive reinforcement: it brings pleasure, a "buzz" or a win.
• Negative reinforcement: it removes something unpleasant, such as stress or withdrawal.
• Through classical conditioning, cues (places, people, times of day) become linked with the reward and can trigger cravings.
• These learning processes explain how peer influence can turn first use into a habit.

Unlearning an addiction

• If an addiction was learned, new learning can change it: therapies try to break the link between the behaviour and its reward and build new habits.
• Aversion therapy uses classical conditioning: the substance is paired with something unpleasant, e.g. a prescribed drug (Antabuse) that causes sickness if alcohol is drunk. The person learns to link alcohol with feeling ill.

Self-management programmes

• Self-management programmes put the person in charge of recovery, e.g. self-help groups such as Alcoholics Anonymous.
• 12-step recovery programmes: admit loss of control, accept help, make amends and support others, often with a mentor.
• Support, shared experience and accountability improve mental health by reducing isolation.
• Holistic approaches treat the whole person; reductionist ones focus on one part, such as a single learned link.

Big ideas

• Everyone has mental health; a significant mental health problem is severe, lasting and gets in the way of daily life, and a clinician makes the diagnosis.
• Recorded rates have risen, partly because of modern challenges such as isolation, partly because problems are better recognised and less stigmatised.
• Mental health problems affect the person (relationships, daily life, physical health) and society (care, health services, the economy).
• Sadness is a normal emotion that lifts; clinical depression is persistent low mood or loss of interest with other symptoms that affect daily life.
• Unipolar depression is only low; bipolar depression alternates with mania.
• ICD symptoms include low mood, reduced energy, changes in sleep and appetite and decreased self-confidence, most days for at least two weeks; the number and severity of symptoms set mild, moderate or severe.
• Biological explanations are the nature side of the debate: depression is linked to an imbalance of neurotransmitters, especially too little serotonin.
• Many psychologists now think a vulnerability (nature) plus stressful events (nurture) together trigger depression: the diathesis–stress idea.
• Psychological (cognitive) explanations say depression comes from how a person thinks about events, learned through experience: the nurture side.
• Negative schemas (the negative triad) and internal, stable, global attributions lead to depression.
• SSRIs block the reuptake of serotonin, so more stays in the synapse; they take weeks to work and can have side effects.
• CBT helps people identify and challenge negative thoughts and change behaviour, building skills that last.
• Wiles et al. found CBT added to medication helped people whose depression hadn't improved with antidepressants alone. Drugs alone are reductionist; combining treatments is more holistic.
• Substance misuse is harmful use; addiction (dependence syndrome in the ICD) adds a strong desire despite harm, difficulty controlling use and a higher priority than other activities.
• Some people inherit genetic vulnerability: Kaij's twin study found higher concordance in identical twins, but well below 100%, so the environment matters too.
• Peer influence (nurture): people observe and imitate friends and are rewarded with acceptance; aversion therapy re-conditions the link, and self-management programmes such as 12-step groups take a holistic approach.
• Addiction that was learned can be changed by new learning, but it takes time and support.