Coma: what it is, what causes it, how long it lasts and what happens next

NHS inform describes a coma as a state of unconsciousness where a person is unresponsive and cannot be woken. The person is alive and may have minimal brain activity, but shows no signs of being aware. Their eyes may be closed, and they may not respond to sound or pain, or be able to communicate or move voluntarily.

Headway adds that a person in a coma may look as if they are asleep but cannot be woken. They do not respond to touch, light or sound and cannot make intentional movements. They may cough or swallow, but these are reflexive and not intentional. Headway defines a coma as loss of consciousness that lasts for longer than 6 hours.

NHS inform says someone in a coma may have very reduced basic reflexes, such as coughing and swallowing. They may be able to breathe on their own, although some people need a ventilator and a breathing tube to keep the airway open.

A coma happens when the brain is so badly affected that it cannot keep a person awake and aware. Headway explains that the brain is responsible for everything we think, feel, say and do, and also for basic functions such as breathing, alertness and sleep-wake cycles. Accidents or illnesses can damage it, for instance by injuring brain structures or causing blood to leak into the brain, and in very severe cases this can lead to a coma.

NHS inform lists injury to the brain such as a severe head injury or stroke, and says there are also a range of other conditions that can cause a coma. Headway gives a serious injury following a road traffic collision, a stroke or an anoxic brain injury (where the brain is deprived of oxygen) as examples of events that can cause loss of consciousness.

Headway also notes that the length of a coma depends on the extent, type and location of the injury. It gives the brainstem as an example: severe damage to this part of the brain can result in the person remaining in a coma.

Neither NHS inform nor Headway can give a firm answer, because every person and injury is different. Headway says nobody can tell how long a coma will last, that in many cases it lasts a few weeks, and that it can be much shorter or longer depending on factors such as the person's age and the extent of the brain injury. NHS inform says the time spent in a coma can vary from days to months, and that some patients never regain consciousness.

NHS inform lists what influences the chance of a full recovery: the severity of the brain injury, its cause, the person's age, how long they have been in a coma and how physically fit they were beforehand. It adds that it is impossible to predict accurately how long a coma will last, whether someone will recover, and if they will have long-term problems.

Headway explains that an induced coma is different from the coma that follows a brain injury. A person is deliberately placed in this state by clinicians using specialist medications. It is temporary and carefully controlled, and may be used to help prevent further damage to the brain and to help with recovery after serious illness or injury.

NHS inform says an induced coma allows the patient to cope with other intensive care procedures, such as being on a ventilator, and is achieved using certain anaesthetic drugs. When the person is woken up, Headway says this is done very gradually by slowly reducing the medications. They may initially appear confused and distressed and might need to be sedated, which Headway describes as a normal procedure.

NHS inform says doctors assess the level of consciousness using the Glasgow Coma Scale and monitor it constantly for signs of improvement or deterioration. In the short term a person in a coma is normally looked after in an intensive care unit (ICU), where treatment includes supporting bodily functions such as breathing and treating the underlying cause of the coma.

In the longer term, NHS inform says staff provide supportive treatment on a hospital ward. This can involve providing nutrition, trying to prevent infections, preventing bedsores by moving the person gently and exercising their joints to stop them becoming tight. If someone is in a coma for a long time, a tracheostomy may be used to keep the airway open, which allows better mouth care and lets the person be moved to a long-term ward.

The NHS describes an ICU as a specialist ward, with normally 1 nurse for every 1 or 2 patients, where equipment such as ventilators, monitors, intravenous lines and feeding tubes support the body until the person recovers. Someone in an ICU is often given painkillers and sedatives because some of the equipment can be uncomfortable.

Headway calls waking up from a coma "emerging". It says it is impossible to tell if and when a person will emerge, and that they will not suddenly sit up and start asking questions like in films. In most cases a person begins to regain consciousness but is very confused at first about where they are and what has happened.

They may also behave unusually, for example shouting, swearing or trying to pull out hospital tubes. Headway says this is a normal and temporary part of recovery known as post-traumatic amnesia, that the person is not intentionally behaving this way and probably will not remember it. NHS inform says people usually come round gradually and may be very agitated and confused to begin with.

Some people make a full recovery and are unaffected by the coma, while others have disabilities caused by brain damage. NHS inform says they may need physiotherapy, occupational therapy, psychological assessment and support while recovering, and some may need care for the rest of their lives. Headway says rehabilitation can help with relearning skills such as walking or talking, and that many people go on to make good recoveries.

Not everyone who is in a coma wakes up fully. NHS inform says a person may gradually wake up and gain consciousness, or progress into a vegetative state or a minimally conscious state. Headway calls these two states prolonged disorders of consciousness (PDOC) and says many people who are initially in a coma progress to one of them.

Headway says it is natural to want to be involved in a loved one's care. You can ask nursing staff whether you can help with basic tasks such as wiping their face or brushing their hair, and you should be involved in discussions about treatment, because families can offer helpful information about the person's wishes and preferences.

NHS inform suggests announcing who you are when you arrive, talking to the person as you normally would, being aware that everything said in front of them might be heard, and showing love and support by sitting and holding their hand. It also suggests keeping a diary of news, family events and information about their care, and says many ICUs already do this.

Headway says some families use familiar stimuli such as favourite music or photographs, which it calls a coma stimulation programme, but there is limited evidence for effectiveness and activities should be introduced under clinical guidance because the person needs rest. It says there is no proven way to help someone wake up, and that movements when touched are more likely to be reflexive than a response. Ask the clinical team which signs to look out for.

Looking after yourself matters too. Headway suggests taking regular breaks from the bedside, accepting help from family and friends, keeping your employer informed, eating well and talking to others about how you feel. NHS inform lists the Brain and Spine Foundation, Headway and ICUsteps as sources of support.

A coma is a medical emergency. The NHS says to call 999 if someone has hit their head and has been knocked out and has not woken up, cannot stay awake or keep their eyes open, has a fit (seizure), or has new numbness or weakness in any part of the body. If you are told to go to A&E after a head injury, the NHS says not to drive yourself there.

If someone you are with is unresponsive and cannot be woken, call 999 and follow the call handler's instructions.

Headway says that in some cases of severe injury continuing treatment may no longer benefit the person, and withdrawal of care may be considered. Decisions are made in the person's best interests, under medical, ethical and legal frameworks, and should involve the family and specialists. If family and clinical team disagree, Headway says the case can be referred to the Court of Protection.

The NHS says that if someone in intensive care cannot give consent, ICU staff will usually decide what they feel is in the person's best interests, and will talk things over with the family whenever possible. If the person had nominated someone to make decisions on their behalf or made an advance decision, this is taken into account.

A coma is normally managed in a hospital emergency department and intensive care unit, because it needs immediate, specialist life support. Rehabilitation afterwards is usually arranged by the hospital team and may take place in a neurological ward or specialist rehabilitation setting.

Some people later use private neurorehabilitation, but the type of rehabilitation and the support organisations named above are the same whichever route is used. Ask the hospital team about rehabilitation options and how they will be arranged.