Overview
Bipolar disorder is a long-term mental health condition that causes extreme changes in mood, energy and activity levels. People experience episodes of depression, with low mood, hopelessness and lack of energy, and episodes of mania or hypomania, with elevated or irritable mood, increased energy, racing thoughts and reduced need for sleep. Between episodes, many people feel well.
Bipolar disorder affects about 1 to 2 percent of people, usually starting in late adolescence or early adulthood. It can have a serious impact on relationships, work and health, and carries a higher risk of suicide. However, with long-term treatment, including mood-stabilising medicines and psychological support, most people can manage their symptoms and lead fulfilling lives.
When to get urgent help
Seek emergency help for thoughts of suicide or self-harm, severe mania with risky behaviour, psychotic symptoms, or symptoms of lithium toxicity (vomiting, diarrhoea, shaking, confusion, unsteadiness).
Causes and risk factors
- Genetics: strong family links; having a parent or sibling with bipolar disorder increases risk significantly
- Brain chemistry and structure differences
- Stressful life events, which can trigger episodes
- Sleep disruption
- Substance use: alcohol, cannabis, stimulants
- Childbirth, which can trigger episodes (postpartum psychosis)
- Some medicines, such as antidepressants without a mood stabiliser, or steroids
How it develops (pathophysiology)
Normal mood regulation
Mood is regulated by networks connecting the prefrontal cortex (planning and control), the limbic system, including the amygdala (emotions), and the hippocampus, along with chemical messengers such as serotonin, dopamine, noradrenaline and glutamate. The brain's internal clock (circadian rhythm) also influences mood, energy and sleep.
What goes wrong
Bipolar disorder involves changes in several systems:
- Neurotransmitter imbalance: mania is linked to increased dopamine activity, while depression is associated with changes in serotonin, noradrenaline and dopamine.
- Emotional regulation networks: imaging studies show the amygdala is overactive and the prefrontal cortex is less able to regulate emotional responses.
- Cellular energy and signalling: changes in mitochondrial function, cell signalling pathways (such as protein kinase C and GSK-3) and calcium signalling affect how neurons respond to stress.
- Circadian rhythm disruption: sleep and body-clock disturbances can trigger episodes, and many people have altered clock gene function.
- Inflammation and stress hormones: raised inflammatory markers and stress hormone (cortisol) changes are common during episodes.
- Kindling: repeated episodes may make future episodes more likely, which is why preventing relapse is important.
Why the symptoms happen
- Mania: increased dopamine and reduced prefrontal control lead to elevated mood, grandiosity, racing thoughts, fast speech, reduced need for sleep, risky behaviour and sometimes psychosis.
- Depression: reduced activity in reward circuits and altered neurotransmitter function lead to low mood, loss of interest, tiredness, poor concentration and suicidal thoughts.
- Mixed features: symptoms of both can occur together, with agitation and distress.
How treatment acts on the mechanism
Lithium affects several signalling pathways, including GSK-3 and inositol, stabilising mood and reducing suicide risk. Valproate and lamotrigine act on sodium channels and glutamate signalling. Antipsychotics (such as quetiapine, olanzapine, aripiprazole) block dopamine receptors, treating mania. Psychological therapies and regular routines stabilise circadian rhythms and help people recognise early warning signs.
Types
- Bipolar I disorder: at least one manic episode, often with depressive episodes
- Bipolar II disorder: at least one hypomanic episode and one major depressive episode, without full mania
- Cyclothymic disorder: long-term milder mood swings
- Rapid cycling: four or more episodes a year
Signs and symptoms
Mania or hypomania:
- Feeling very happy, excited or irritable
- Increased energy and activity
- Needing much less sleep
- Talking quickly, racing thoughts
- Easily distracted
- Feeling unusually important or powerful
- Risky behaviour: spending, sex, driving, substance use
- Psychotic symptoms in severe mania (delusions, hallucinations)
Depression:
- Low mood, hopelessness
- Loss of interest or pleasure
- Tiredness and low energy
- Sleep and appetite changes
- Poor concentration
- Feelings of guilt or worthlessness
- Thoughts of death or suicide
How it is diagnosed
- Assessment by a psychiatrist based on history of mood episodes
- Information from family or friends
- Mood charts or diaries
- Physical examination and blood tests to exclude thyroid problems, substance use and other causes
- Screening questionnaires
Possible complications
- Suicide and self-harm
- Substance misuse
- Relationship, work and financial problems
- Legal problems during mania
- Physical health problems, including heart disease and diabetes
- Side effects of medicines
Goals of treatment
Treatment aims to treat acute episodes, prevent future episodes, reduce suicide risk and support recovery and quality of life.
Medicines
- Lithium: first-line long-term mood stabiliser
- Valproate: avoided in women who could become pregnant because of serious risks to the baby
- Lamotrigine: particularly for preventing depression
- Antipsychotics: quetiapine, olanzapine, aripiprazole, lurasidone, cariprazine
- Antidepressants only with a mood stabiliser, because they can trigger mania
Other treatments
- Psychoeducation: understanding the condition and warning signs
- Cognitive behavioural therapy
- Family-focused therapy
- Interpersonal and social rhythm therapy
- Regular sleep and daily routines
- Crisis plans
- Electroconvulsive therapy (ECT) for severe episodes
- Hospital care during severe episodes
Living with it and prevention
- Take medicines regularly, even when well
- Keep regular sleep patterns
- Avoid alcohol and recreational drugs
- Learn your early warning signs
- Manage stress
- Stay connected with support networks
- Have a crisis plan
Monitoring and follow-up
People taking lithium need regular blood tests to check lithium levels, kidney and thyroid function. Weight, blood sugar and cholesterol are monitored with antipsychotics. Regular reviews track mood and side effects.
Outlook
Bipolar disorder is long-term, but many people manage it well with treatment and support, leading full lives.
Learning personal early warning signs, keeping a regular sleep routine and having a written plan for what to do when mood changes can prevent many relapses. Family members can be part of this plan, and regular review with the care team helps keep treatment on track over the years.
Special considerations
- Pregnancy: needs careful planning; the risk of relapse after birth is high
- Young people: may be misdiagnosed with depression or ADHD
- Older adults: may need lower medicine doses
