Mental Health - Discover the latest research in our continuously updated special report.
When the heart breaks down, it beats erratically or not at all. A bone can chip or snap. But when the complex network of neurons in our brain malfunctions, the result can be a near-endless variety and combinations of mental illnesses.
It’s normal to sometimes be sad, happy, anxious, confused, forgetful or fearful, but when a person’s emotions, thoughts or behaviour frequently trouble them, or disrupt their lives, they may be suffering from mental illness. According to the World Health Organization (WHO), about 450 million people worldwide are affected by mental, neurological or behavioural problems at any time.
However, determining that someone has a mental illness, and which one, is one of the challenges psychiatrists face. One effort to catalogue these afflictions is the "psychiatrists' bible", the Diagnostic and Statistical Manual of Mental Disorders - the latest edition fills nearly one thousand pages and lists over 400 disorders.
Diversity of disorders
Among the best known and most common mental illnesses is depression - a prolonged, debilitating sadness, sometimes accompanied by a feeling of hopelessness and thoughts of suicide. Seasonal affective disorder is a type of depression that affects some people in the autumn and winter and is triggered by the shrinking hours of daylight and colder temperatures. In bipolar disorder, a person swings from depression to episodes of mania where they are euphoric, energetic and unrealistically confident in their abilities.
Personality disorders are behaviour patterns that are destructive to the person themselves or those around them. In dissociative disorders, someone experiences a sudden change in consciousness or their concept of self. In dissociative amnesia, for example, the result is a loss of part or all of their memories. Samson, the Biblical strongman, may have suffered from the earliest recorded case of antisocial personality disorder.
Anxiety disorders are characterised by powerful feelings of stress and physical signs of fear - sweating, a racing heart - due to some cue in the environment, or for no obvious reason at all. These include post-traumatic stress disorder, panic disorder, obsessive compulsive disorder, anger disorders, hypochondria, social phobia, and other phobias including agoraphobia (open spaces), claustrophobia (small spaces), acrophobia (heights), and arachnophobia (spiders).
Enormous cost
Eating disorders involve an unhealthy relationship to food. A sufferer of anorexia nervosa will strive for thinness to the point of starvation, due to a distorted perception of their body and dissatisfaction in their sense of control. People with bulimia engage in cycles of gorging themselves and then purging through vomiting or use of laxatives. Muscle dysmorphia is sometimes thought of as a "reverse" form of anorexia that affects bodybuilders. Sufferers constantly worry that they are too puny, despite being extremely muscular.
Attention-deficit hyperactivity disorder in among the most common mental illness diagnosed in children, affecting their ability to focus and is associated with high levels of activity and impulsiveness.
Mental illnesses are quite common. As many as one in five people are thought to suffer from mental illness, at least temporarily, each year. Suicide - often the result of untreated mental illness - claims 873,000 lives around the world each year. The economic costs of these conditions are also enormous and growing. According to the WHO, depression is expected to account for more lost years of healthy life than any other disease by 2030, except for HIV/AIDS.
Even so, the mentally ill face stigma and discrimination. Studies find people are reluctant to admit they have a mental illness, to seek help, or to stick with treatment. Others are eager to reject the label of a mental illness. For example, some people with autism - characterised by difficulty communicating or socialising - insist the condition is not a disorder that needs to be cured, but just part of normal human "neurodiversity".
Underlying causes
Historically, some symptoms of mental illness, such as erratic behaviour and hearing voices, have been taken as evidence of heavenly communication or demonic possession.
More recently, brain scans have directly linked these conditions with changes in levels of neurotransmitters - chemicals that convey messages across neurons - or alterations in the number or structure of neurons in different brain areas. For instance, people suffering from depression often display lowered levels of the neurotransmitter serotonin.
In a few cases, the immediate cause of the malfunction has been identified. Alzheimer’s disease, a major source of dementia and memory loss in the elderly, is caused by the accumulation of protein plaques which choke neurons in the brain.
Some infectious diseases can also develop into a menal illness. Untreated HIV infection can cause dementia, as can the uncontrolled replication of the microbe that causes syphilis. Borrelia burgdorferi - the Lyme disease bacterium, the Borna disease virus and the toxoplasma parasite, responsible for malaria, are also thought capable of triggering a variety of mental illnesses.
In many cases the precise cause is unclear and experts suspect that many different factors are involved. One striking example is schizophrenia, distinguished by psychosis. This is a distorted view of reality, which may include hallucinations, hearing voices, delusions, and paranoia. The chance that identical twins both develop schizophrenia is much higher than that for fraternal twins or siblings, arguing for the strong role of inherited genes. But scientists are accumulating a growing list of other risk factors that predispose people to this condition, including prenatal exposure to famine conditions, certain infections or exposure to lead. The season of their birth also seems important - birth in winter or early spring increases the risk, as does an older father and, controversially, child abuse.
Genes are also thought to influence many other mental health problems, including: anorexia, autism, Alzheimer's disease and bipolar disorder,
Some other factors that have been linked to mental illness include the womb environment,exposure to X-rays, being held in detention centres and an having an overactive immune system.
Some researchers believe that smoking cigarettes and taking recreational drugs like LSD, ecstasy and cannabis, may elevate a user’s risk of mental illnesses, including schizophrenia - although it can be difficult to assess whether drug use is a cause or effect. And careful use of LSD and ecstasy might even help treat psychiatric problems.
Psychiatric treatments
Psychiatric treatment for mental illness can take many forms. In psychotherapy, the patient is encouraged to recognise their problems, understand what may trigger undesirable behaviour, and develop coping strategies.
Many medications are also available to treat some of the most severe symptoms. Mood-stabilising drugs aim to moderate manic episodes of bipolar disorder and may also reduce recurrences of depression. Antipsychotics reduce the reality-bending symptoms of schizophrenia. Anti-depressants include drugs like Prozac - known as selective serotonin reuptake inhibitors or SSRIs - which slow the removal of serotonin in the brain, thus increasing the neurotransmitter's availability.
Recently, however, some experts think there has been a rush to medicate every disorder and have questioned the effectiveness of many drugs. There is also controversy about using these drugs - such as Ritalin or amphetamines - to treat children.
Other less mainstream treatments for mental health problems, include stimulating the brain with magnetic pulses, electroconvulsive therapy, deep brain electrode stimulation, staying at a Hindu temple and using virtual reality to treat schizophrenia and phobias. Some experts argue that the different treatments for depression share a common mechanism - prompting the growth of neurons.
Madly creative
Madness has long been linked with genius. Many famous artists, writers and scientists have suffered from mental disorders, leading some to wonder if there is a link between these illnesses and creativity.
The mathematician John Nash struggled with schizophrenia while he developed the theory that earned him a Nobel Prize. The artist Vincent Van Gogh, the composer Robert Schumann and the writer Fyodor Dostoevsky are said to have suffered from a range of mental disorders including hypergraphia, a compulsion to write - a sign perhaps their art emerged from an unrelenting urge to communicate.
One possibility is that genes that predispose people to such devastating illnesses persist because when the syndromes are present in a milder form, this heightened creativity gives people an evolutionary advantage.
