Schizophrenia — Causes, Symptoms & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Schizophrenia is a severe, chronic mental disorder characterised by disruptions in thought, perception, emotion, language, sense of self, and behaviour. It has a lifetime prevalence of 0.3–0.7% globally, affecting approximately 24 million people. The disorder typically emerges in late adolescence or early adulthood — onset in men is usually between 18–25 years; in women, 25–35 years, with a second peak after 40. Although schizophrenia is not the most common mental disorder, it contributes disproportionately to disability globally, accounting for nearly 7.4% of all disability-adjusted life years (DALYs) caused by mental disorders. Positive symptoms (hallucinations, delusions, disorganised thinking), negative symptoms (social withdrawal, blunted affect, avolition, poverty of speech), and cognitive impairment define the clinical picture. With appropriate treatment — antipsychotic medication, psychological therapy, and psychosocial rehabilitation — many people with schizophrenia lead meaningful lives, though complete symptom-free recovery remains rare.

Schizophrenia has a complex, multifactorial aetiology involving genetic vulnerability interacting with environmental stressors — the stress-vulnerability (diathesis-stress) model. Genetic factors: heritability is approximately 80% — first-degree relatives have 10-fold increased risk; concordance in identical twins is 40–50% (indicating non-genetic factors are essential). Polygenic architecture — hundreds of common variants (many in genes affecting synaptic plasticity and dopamine signalling) plus rare copy number variants (22q11.2 deletion syndrome causes schizophrenia in 25%). Neurodevelopmental: prenatal insults — maternal infection during second trimester (influenza, Toxoplasma gondii, rubella), obstetric complications, malnutrition, and winter or spring birth (possibly related to prenatal viral exposure). Dopamine hypothesis: dysregulation of mesolimbic dopamine pathway (excess dopamine causing positive symptoms — supported by antipsychotic D2 receptor blockade efficacy) and mesocortical pathway deficit (negative symptoms and cognitive impairment). Cannabis use: heavy adolescent cannabis use (particularly high-THC, low-CBD varieties) increases schizophrenia risk 3–5 fold — especially in genetically predisposed individuals. Social and environmental: urban birth and upbringing, migration (particularly minority ethnic groups in predominantly White societies), social adversity, childhood trauma, and social isolation all increase risk.

Schizophrenia symptoms are classified into three domains. Positive symptoms (excess of normal function): hallucinations — auditory hallucinations (voices commenting, arguing, giving commands — characteristic of schizophrenia; 75% of patients), visual, tactile, or olfactory hallucinations; delusions — fixed false beliefs not amenable to reason (paranoid persecution delusions, ideas of reference, delusions of control — thought insertion, thought withdrawal, thought broadcasting, passivity experiences); disorganised thinking (formal thought disorder — derailment, tangentiality, word salad). Negative symptoms (reduction in normal function): blunted or flat affect (reduced emotional expression), alogia (poverty of speech), avolition (inability to initiate and persist in goal-directed activities), anhedonia (reduced ability to experience pleasure), asociality. Cognitive symptoms: impaired working memory, attention, executive function, and processing speed — these correlate with functional outcomes and respond poorly to antipsychotics. Prodromal phase: attenuated psychosis symptoms, social withdrawal, decline in academic or occupational functioning — often precedes first episode by months to years. DSM-5 diagnosis requires two or more core symptoms for at least one month, with social or occupational dysfunction for at least six months.

Schizophrenia is a clinical diagnosis — there is no diagnostic blood test or brain scan. Psychiatric assessment: structured clinical interview assessing the DSM-5 or ICD-11 criteria — minimum two of: delusions, hallucinations, disorganised speech, grossly disorganised or catatonic behaviour, or negative symptoms — present for at least 1 month (active phase), with signs of disturbance for at least 6 months (including prodrome). PANSS (Positive and Negative Syndrome Scale): 30-item rating scale quantifying positive, negative, and general psychopathology. Mandatory exclusion of organic causes: full blood count (FBC), thyroid function, vitamin B12 and folate, HbA1c, liver and renal function, CRP, syphilis serology (VDRL), HIV, urine drug screen (cannabis, stimulants, cocaine can mimic psychosis), urinalysis. Brain MRI: to exclude structural causes (tumour, encephalitis, demyelination, temporal lobe epilepsy). Anti-NMDA receptor encephalitis (anti-NMDAR antibodies) must be considered in young women with first episode psychosis — produces psychosis, seizures, and autonomic instability, but is treatable. EEG: if epilepsy (temporal lobe seizures) is suspected. Differential diagnoses: bipolar disorder with psychotic features, psychotic depression, schizoaffective disorder, drug-induced psychosis, medical causes.

Antipsychotic medication is the cornerstone of treatment. Second-generation antipsychotics (SGAs — atypical): risperidone 4–6 mg/day, olanzapine 10–20 mg/day, quetiapine 400–800 mg/day, aripiprazole 15–30 mg/day, paliperidone, amisulpride — block dopamine D2 and serotonin 5-HT2A receptors; fewer extrapyramidal side effects than first-generation; weight gain and metabolic syndrome are significant concerns (olanzapine, clozapine highest risk). First-generation antipsychotics (FGAs — typical): haloperidol, chlorpromazine — effective but higher rates of extrapyramidal side effects (EPSEs — parkinsonism, akathisia, tardive dyskinesia — especially concerning with long-term use). Clozapine: the most effective antipsychotic, reserved for treatment-resistant schizophrenia (failure of two adequate antipsychotic trials) — approximately 30–60% respond. Requires mandatory blood monitoring (weekly initially, monthly thereafter) for agranulocytosis (1–2% incidence). Effective for both positive and negative symptoms and suicide risk reduction. Long-acting injectable antipsychotics (depot formulations — LAIs): paliperidone palmitate monthly, risperidone microspheres, aripiprazole lauroxil — eliminate adherence uncertainty; associated with 60% reduction in relapse vs. oral formulations. Psychological therapies: Cognitive Behavioural Therapy for psychosis (CBTp) — NICE-recommended; reduces positive symptom distress and improves insight; 16–20 sessions individually or in groups. Family intervention therapy (FIT) — reduces relapse rate by 50% by reducing high expressed emotion (EE) within the family. Social skills training, supported employment (Individual Placement and Support — IPS), and cognitive remediation for cognitive impairment. Early intervention in psychosis (EIP) services: dedicated teams for first-episode psychosis — crucial for minimising delay to treatment; duration of untreated psychosis (DUP) is the most modifiable predictor of outcome.

Schizophrenia carries substantial short and long-term complications. Suicide is the leading cause of premature death — lifetime risk is 5–10% (approximately 20–40 times the general population rate); risk is highest during the first 5 years of illness and in the period around discharge from inpatient care; clozapine is the only medication proven to reduce suicidality in this population. Premature mortality: people with schizophrenia die 15–20 years earlier than the general population, predominantly from cardiovascular disease — driven by metabolic syndrome from antipsychotics (especially olanzapine and clozapine), sedentary lifestyle, heavy smoking (above 60%), and insufficient access to physical healthcare. Cognitive impairment (working memory, processing speed, executive function, sustained attention) is intrinsic to schizophrenia and is the strongest predictor of functional outcomes — it does not respond well to antipsychotics. Social disability — unemployment, social isolation, and homelessness — affects a large proportion. Tardive dyskinesia (involuntary oro-facial and limb movements) from long-term antipsychotic use affects 20–30%, and may be irreversible. Secondary substance misuse worsens prognosis in up to 50% of patients.

Primary prevention is not currently possible given the complex genetic architecture, but risk reduction is achievable: avoidance of heavy cannabis use (particularly in adolescence and early adulthood) is the single most modifiable lifestyle risk factor. Early intervention: identification and treatment of the prodromal phase ('ultra high risk' individuals) with CBT and low-dose antipsychotics may delay or prevent onset of first episode psychosis. Secondary prevention (preventing relapse): maintain antipsychotic medication — the most critical factor (most relapses occur after stopping medication); attend regular psychiatric follow-up; engage family in psychoeducation to reduce expressed emotion; avoid substance misuse (cannabis, stimulants, alcohol trigger relapse); maintain regular sleep-wake cycle and structured daily routine. Physical health monitoring: people with schizophrenia die 15–20 years earlier than the general population, predominantly from cardiovascular disease — monitor weight, blood pressure, glucose, and lipids annually; smoking cessation support (more than 60% of people with schizophrenia smoke).

Call emergency services or go to the nearest emergency department immediately if a person with schizophrenia is threatening to harm themselves or others, expresses suicidal intent (suicide risk is 5–10% lifetime in schizophrenia — significantly elevated), or is in an acute psychotic crisis with severe agitation. Contact your community mental health team (CMHT) urgently for: sudden worsening of psychotic symptoms, stopping medication without medical guidance, significant change in behaviour or thought (neighbour reports, family concern), or marked deterioration in self-care. If you are a worried family member, do not wait for the person to ask for help themselves — contact their psychiatrist or CMHT. For anyone with no psychiatric history developing new-onset psychosis for the first time (hallucinations, strange beliefs, behaviour change), refer to early intervention in psychosis services immediately — duration of untreated psychosis (DUP) is the strongest modifiable predictor of long-term outcome.