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.
• The mental health continuum runs from good to poor; people move along it over time.
• A clinician makes a diagnosis using ICD (the International Classification of Diseases).

How common, and who is most affected?

• Prevalence: 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). For ages 16 to 64 it rose from 15.5% in 1993 to 22.6%.
• Incidence is how many new cases appear over a period of time.

Why recorded rates change

• 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.
• Changing classification: ICD is revised, adding and removing categories. Homosexuality was removed in 1990.

Attitudes, stigma and discrimination

• Stigma is negative attitudes and stereotypes; discrimination is unfair treatment because of them.
• Before diagnosis, fear of being judged can stop someone seeking help, so problems get worse.
• After diagnosis, a label can bring exclusion, unfair treatment at school or work, and self-stigma (believing the stereotypes).

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.
• Since the asylums closed, support is mainly care in the community: at home, in day centres or supported housing. It depends on local services and funding.

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.

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.

Key statistics on depression

• Figures depend on how depression is measured and who is asked.

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.

Social rank theory

• Social rank theory is an evolutionary explanation: depression evolved because it helped our ancestors survive in groups.
• Group members compete for rank (status). After losing, low mood makes the loser accept a lower rank: they stop challenging, withdraw and submit.
• This reduces conflict: the winner stops attacking, so the loser avoids injury and stays in the group.
• Today, defeat or rejection may trigger this response, which fails to switch off.

Reductionism and holism

• Reductionism explains behaviour by breaking it down to one simple cause or level, eg genes, chemicals or one evolved response.
• Holism looks at the whole person: biology, thinking, relationships and life situation together.
• Social rank theory is reductionist: it reduces depression to one evolved reaction to losing status and ignores thinking, upbringing and brain chemistry.
• Reductionist theories are easier to test; holistic accounts may fit real lives better.

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.

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.

The ABC model

• Ellis's ABC model: an Activating event happens → a Belief about it → a Consequence (feelings and behaviour).
• It is B, not A, that causes C.
• Rational beliefs are flexible and realistic: "I wanted to pass, but failing isn't the end of the world."
• Irrational beliefs are rigid and extreme: "I must pass or I'm worthless." These lead to depression.

Free will or determinism?

• Determinism: behaviour is caused by things we can't control, eg genes or upbringing.
• Free will: people can choose how they think and act.
• The ABC model leans towards free will: people can learn to challenge and change irrational beliefs, which is why therapy based on it can work.
• Criticism: beliefs may themselves be determined by upbringing, and the model can seem to blame people for their depression.

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.

Psychotherapy

• Psychotherapy means treating a mental health problem by talking with a trained therapist, rather than with medication.
• Types used for depression include CBT, interpersonal psychotherapy (improving relationships) and problem-solving therapy.
• It improves mental health by helping people understand their thoughts and feelings, change unhelpful patterns and build coping skills that last after therapy ends.

Studying depression: neuropsychology

• Neuropsychology studies how the brain relates to thinking and behaviour.
• Neuropsychological tests are standard tasks measuring memory, attention and planning. They can show which thinking skills depression affects.
• Brain imaging, eg fMRI and PET scans, shows activity in a living brain. Researchers compare people with and without depression, or before and after treatment.
• Scans add to older methods such as post-mortem studies, which could examine the brain only after death.

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.

Hearing a voice when no one is there: what is the brain doing?

What is schizophrenia?

• Schizophrenia is a severe mental illness that changes how a person experiences reality.
• Positive symptoms add experiences: hallucinations (hearing, seeing or feeling things that are not there) and delusions (fixed false beliefs held despite evidence).
• Disorganised thinking and speech.
• Negative symptoms take away: social withdrawal, low motivation, flat emotion.
• In the ICD (the International Classification of Diseases), symptoms last at least a month. A clinician makes the diagnosis.

Schizophrenia: key statistics

• Suggested reasons for these differences include discrimination, bias in services, barriers to getting help and wider inequalities.
• England's 2023/4 survey found no significant ethnic difference after allowing for age, but cases were few.

The dopamine hypothesis

• Neurons pass signals across synapses using neurotransmitters. Dopaminergic neurons release dopamine.
• The dopamine hypothesis: in schizophrenia the dopamine system is overactive. Too much dopamine is released, or receptors are too many or too sensitive, causing high dopamine levels.
• This is thought to cause positive symptoms such as hallucinations.
• Evidence: drugs that raise dopamine, e.g. amphetamine, can cause psychosis-like symptoms; drugs that block dopamine receptors reduce them.

Brain structure and activity

• Frontal lobes: lower activity during thinking tasks, linked to poor planning and negative symptoms.
• Temporal lobes: process sound and language; differences here are linked to hearing voices.
• Hippocampus: often smaller, linked to memory problems.
• Brain volume: often reduced overall, with larger fluid-filled spaces (ventricles).
• Neurological damage, e.g. complications at birth or head injury, may raise the risk.

Psychosis like schizophrenia is linked to poverty. Which causes which?

Poverty and psychosis: which way round?

• Psychotic disorders, including schizophrenia, are more common among adults in the most deprived neighbourhoods and adults out of work (NHS England 2025).
• This is a correlation: on its own it can't show which causes which.
• Social causation: the stress of poverty raises the risk of becoming ill.
• Social drift theory: the illness comes first, and its effects push the person down the social scale.

How the drift happens

• Symptoms usually begin in the late teens or twenties, while people are studying or starting work.
• Rejection by society: stigma and discrimination make it harder to keep a job, a home and friends.
• Disengagement of the individual: the person withdraws, e.g. through low motivation, and stops work, study and social contact.
• With less income, the person drifts into poorer housing and areas.

Antipsychotics at the synapse

• Antipsychotics are usually the first treatment for an acute episode (NHS 2023).
• Most block dopamine receptors on the receiving neuron, so less dopamine signal crosses the synapse. Newer (atypical) ones also act on other neurotransmitters, such as serotonin.
• This reduces positive symptoms like hallucinations, usually over days or weeks.
• Limitation: side effects such as weight gain and drowsiness, and movement problems with older types.

Psychotherapy for schizophrenia

• Psychotherapy (talking therapy) is usually offered alongside medication.
• CBT helps the person spot thinking patterns behind distressing feelings, recognise delusional thinking and avoid acting on it.
• Family therapy helps the family understand the illness and plan for crises.
• It improves mental health by reducing distress and helping the person re-engage with work, study and friends, working against drift.

Neuropsychology: studying the brain

• Neuropsychological tests measure thinking skills, e.g. the Wisconsin Card Sorting Test for planning and flexible thinking, a frontal lobe task.
• Early research relied on examining brains after death. Brain imaging now studies living brains:
• Structural scans (CT, MRI) show brain volume, e.g. a smaller hippocampus.
• Functional scans (PET, fMRI, SPECT) show activity during a task, as in Daniel et al. (1991).

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.
• About 1 in 5 adults in England has a common mental health condition, more often women, young adults and LGB people; classification and attitudes have changed since the Mental Health Act 1959.
• 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.
• 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.
• About 4% of adults in England have a depressive episode at any one time (NHS England 2025), more often women, and about half of those finishing NHS talking therapies recover (2024 to 2025).
• Biological explanations are the nature side of the debate: social rank theory says depression evolved to make a defeated group member accept a lower rank and so reduce conflict.
• Social rank theory is reductionist: it leaves out thinking, upbringing and brain chemistry.
• 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.
• In the ABC model, irrational beliefs (B) about an activating event (A) lead to depression.
• The ABC model leans towards free will (beliefs can be changed), though beliefs may be determined by upbringing. Tandoc et al. (2015) found Facebook use was linked to depression only through envy.
• SSRIs block the reuptake of serotonin, so more stays in the synapse; they take weeks to work and can have side effects.
• Psychotherapy, such as CBT, helps people identify and challenge negative thoughts and change behaviour, building skills that last.
• Neuropsychological tests and brain scans (fMRI, PET) let researchers study how depression affects the brain and thinking.
• Schizophrenia is diagnosed by a clinician using the ICD: positive symptoms (hallucinations, delusions, disorganised thinking) and negative symptoms (withdrawal, low motivation); about 1 in 300 people worldwide, onset usually late teens to twenties, and at least 1 in 3 recover fully.
• The dopamine hypothesis: an overactive dopamine system causes high dopamine levels; the frontal lobes, temporal lobes and hippocampus differ in volume and activity, and Daniel et al. (1991) linked dopamine to prefrontal function.
• The biological theory is on the nature side of the nature/nurture debate; environmental triggers matter too.
• Social drift theory: the illness comes first, then rejection by society and disengagement push the person down the social scale; the main criticism is that a correlation can't establish cause and effect.
• Antipsychotics block dopamine receptors at the synapse and reduce positive symptoms; psychotherapy such as CBT and family therapy reduces distress and helps people re-engage.
• Neuropsychology studies schizophrenia with tests such as the Wisconsin Card Sorting Test and with structural (CT, MRI) and functional (PET, fMRI, SPECT) brain imaging.