- Depression is a very common mental health problem worldwide. It is estimated that it will become the second most common cause of disability, after heart disease, by 2020 
- The term ‘depression’ covers a very wide range of experiences and level of illness forms, from mild to severe, transient to persistent.
- A distinction should be made between ‘unipolar’ forms of depression such as major depression and dysthymia which involve persistent, low moods, and manic or ‘bipolar’ depression which involves bouts of low moods followed by extreme ‘highs’ or mania.
- Unipolar forms of depression are more common in women than men. In Britain, 3-4% of men and 7-8% of women suffer from moderate to severe depression at any one time .
- Bipolar depression affects men and women equally, and afflicts about 5 people in 1000. 
- For people with severe depression, the lifetime risk of suicide may be as high as 6%  This compares with a risk of 1.3% in the general population 
- For those with bipolar, suicide risks are high, at 15 times that of the general population. 
- Antidepressants can be very effective in helping people to recover from depression, but can also be used to attempt suicide through an overdose. There is no evidence to show that they reduce suicide or self harm. 
- Selective Serotonin Reuptake Inhibitors have been investigated as antidepressant drugs which can cause suicidal thoughts and behaviour in some people. Current research suggests that this is true for children and adolescents but there is no evidence to support the heightened suicide risk in adults. 
- Symptoms of depression appear over a period or in the case of manic depression, suddenly and escalate over a few days.
2. Clinical symptoms and diagnostics
The following are amongst the symptoms cited in cases of major depressive episodes. It is worth noting that these usually develop over days to weeks. In diagnostic terms, five of these should be present during the same two-week period and have caused a change from previous functioning. For a major depressive episode, symptoms must appear on a daily basis and last most of the day or all day.
- Depressed mood (such as feeling sad, empty).
- Markedly diminished pleasure in all (or almost all) activities
- Insomnia (or hypersomnia)
- Increase / decrease in appetite or significant weight loss
- Fatigue / loss of energy
- Feelings of worthlessness
- Excessive or inappropriate guilt
- Diminished ability to think, concentrate, and/or take decisions
- Recurrent thoughts of death, suicidal ideation, having a suicide plan or making a suicide attempt.
Manic episodes typically occur suddenly and symptoms escalate over the course of a few days. In diagnostic terms a person should be experiencing persistently elevated mood for at least one week with three or more of the following symptoms persisting:
- ‘Racing’ of ideas’
- More talkative than usual
- Inflated self-esteem
- Significantly reduced need for sleep
- Great difficulties concentrating
- Engagement in activities which appear pleasurable but can lead to painful consequences
3. Definitions and types of depression
- The term depression covers a wide range of experiences and illnesses, from mild to severe, transient to persistent. Medical classifications and terms are:
- Major depressive disorder – this is more severe and is diagnosed by the person feeling five or more of the symptoms of depression, lasting over two weeks.
- Adjustment disorder – these are milder and shorter-lived forms of depression, often resulting from stressful experiences.
- Dysthymia – covers long-term symptoms of depression (of at least two years) which are not severe enough to meet the criteria for major depression.
- Post-natal depression – which can occur after childbirth (and also peri-natal depression, which can occur during pregnancy but which is less common).
- Seasonal Affective Disorder (SAD) – which is depression associated with lack of daylight and shorter daylight hours in winter.
- Bipolar disorder (also sometimes called manic depression, or bipolar affective disorder). See below. 
- A distinction should be made between the forms of depression which are ‘unipolar’ including major depression, dysthymia, SAD, and post-natal depression, and ‘bipolar’ disorder or manic depression. Bipolar depression is a serious mental health problem involving extreme swings of mood (highs and lows). This form of depression occurs in bouts, separated by periods of mania (highs), in which the person may become psychotic and lose touch with reality. 
- A persistent “low” mood, with difficult feelings such as guilt, anxiety, sadness,
- losing interest or pleasure in things, low self-esteem;
- difficulty sleeping or sleeping too much;
- tiredness, fatigue;
- changes to appetite, and perhaps loss or gain of weight;
- difficulty in thinking or concentrating;
- recurrent thoughts of death or suicide attempt. 
- Depression can be due to a shortage of certain chemicals (serotonin, noradrenaline and dopamine) in the brain, which can be triggered in some people by stress. 
- The presentation of depression, its meanings and how it is experienced, vary according to culture. The western experience of depression, outlined above, may not hold for people of Asian, Caribbean or other cultures. 
4. Prevalence of unipolar types of depression
- Depression is a very common mental health problem worldwide. The World Health Organisation estimates that depression will become the second most common cause of disability worldwide (after heart disease) by 2020. 
- In total, about one in six adults are known to have a neurotic mental health disorder in any given week. The most common disorder is mixed anxiety and depression (8.8%) 
- Major depression affects 1 in 20 people during their lifetime. Both major depression and dysthymia appear to be more common in women. 
- In Britain, 3-4% of men and 7-8% of women suffer from moderate to severe depression at any one time. 
- Women are twice as likely to be diagnosed and treated for depression. However, it is believed that men suffer depression to a larger extent that the statistics show, since men are less likely to seek medical help and when they do, doctors are less likely to detect depressive symptoms. 
- In North America, increased use or abuse of alcohol and other drugs amongst men is now being viewed as a “masked” symptom of depression. 
- Only 20% of people suffering from depression actually go to their doctor with an emotional problem. The vast majority complain of nonspecific symptoms such as headache, tiredness or vague abdominal pains. This type of “masked” depression is more common in older people, who may feel embarrassed about their condition. 
- An international study in 10 countries found that rates of major depression in the community varied from 1.5% in Taiwan to 19% in Beirut. The average age when people began to experience depression was between 25 and 35 years. In every country, rates of major depression among women were higher than those among men. 
- Depression is the most common psychiatric disorder in later life. 10 -15% of the population aged 65 years or over suffer from significant depressive symptoms. 
- Depression is relatively rare in children. Prevalence figures for major depression are 0.3% in pre-school children, 1.8% before puberty, and 5-9% in adolescents. The female:male gender ratio is equal prior to puberty but among adolescents depression is more common in females. 
- Dysthymia tends to develop early in a person’s life during childhood to early adulthood, but most people delay approximately 10 years before seeking treatment. Like all forms of unipolar depression, dysthymia affects more women than men. At any point in time, 3 – 5% of the population may be affected with dysthymia, within a lifetime approximately 6% are affected. 
- In western Europe the prevalence for post-natal depression is 13% 
5. Prevalence of bipolar depression
- Bipolar depression is rarer than unipolar forms, and affects men and women equally and affects about 5 people in 1000, or 0.5% of the population in the UK. It often first occurs when work, study, family or emotional pressures are at their greatest. In women it can also be triggered by childbirth or during the menopause. 
- Age at onset of bipolar disorder is earlier than that for major depression. Research suggests it starts six years earlier .
6. Suicide risk
- For people diagnosed with major depression, the lifetime risk of suicide may be as high as 6% , although this figure may be more applicable to those who have been admitted to hospital as a result of depression. For people seen as outpatients or treated by GPs, risks are much lower 
- For those with bipolar disorder the suicide risk is much higher, at 15 times that of the general population. This risk is further increased by a previous suicide attempt and by alcohol abuse. 
- Every week 10% of the UK population aged 16-65 report significant depressive symptoms, and one in 10 of these admits to suicidal thinking. 
- Previous self-harm
- Severity of the illness
- Alcohol or drugs abuse
- Serious or chronic physical illnesses
- Schizophrenia 
- Research shows that depression is one of the most frequent mental health problems in people who die by suicide. , . This is also true of young people; major depression is common amongst adolescents who have overdosed. 
- Other factors may be important, either independently or in combination with depression, in the development of suicidal thoughts and behaviour in an individual. Such factors include impulsiveness, aggressiveness, addiction, suicide or suicide attempts in close relatives, divorce, separation and parental discord. 
- Depression is common amongst people who self-harm, both in those who habitually self-harm by for example, self-cutting, without suicidal intent  and in those who may have suicidal intent when they self-harm 
- In people who have self-harmed, depression and impulsivity have been shown to be strongly associated with the strength of the intent to die by suicide. 
- Major, or severe, depression in adolescence is associated with higher risk of both suicide attempting and death by suicide in adulthood. 
- Although dysthymia in itself is not related to suicide, 10% of those suffering from it will go on to develop major depression. 
- Severe postnatal depression is linked to elevated suicide risk, despite the fact that in general, women who have recently given birth are at low risk of suicide. Those who are admitted to hospital for very severe post-natal depression can be up to 70 times as likely to die by suicide. Risks are especially high in the first year after childbirth. 
- Depression is generally recognised as a feature of suicide in schizophrenia, where the greatest risk of suicide comes during non-psychotic, depressed phases of the illness . In a survey of 390 schizophrenia patients over a 13 year period, 19 (5%) took their own lives. . However research suggests that the seriousness of suicidal intent is related to hopelessness about the future, which is one particular aspect of depression  .
7. Antidepressants and suicide
Antidepressants are the main mode of treatment for depression by general practitioners, and their usage continues to increase. Annually in the UK, GPs spend £160m per year on antidepressant drugs.  In 2002 33 million prescriptions were dispensed in the UK (16 million in 1995) 
- Whereas many depressed people are helped to recovery by medication, and the rise in prescribing of antidepressants coincides with a fall in national suicide rates, there is as yet no convincing evidence that antidepressants prevent suicide , .
- It is also common for people to kill themselves by overdosing on antidepressants, 15% of overdoses involve antidepressant medication  and there were substantial increases in self-poisoning with antidepressants between 1985 and 1997 in the UK. 
- Using antidepressants to overdose is more common in people who repeatedly self-harm or attempt suicide, and in older people .
- Since depression is such a common factor in suicide, a study on the small Swedish island of Gotland attempted to measure the effects on suicide rates of intensively educating GPs to recognise and treat suicide with antidepressants. Results suggested that the programme resulted in a decrease in suicides in depressed women but no change in suicide rates in depressed men . However, further research in England failed to replicate these effects. , 
8. Selective Serotonin Reuptake Inhibitors and Suicide
Newer antidepressants, called Selective Serotonin Reuptake Inhibitors (SSRIs), have lower mortality in overdose (whether purposeful or accidental) than older drugs.  Older antidepressants include tricyclics and monoamine oxidase inhibitors (MAOIs)
- There has been some controversy over the relation between SSRIs and suicidal thoughts and behaviour, particularly in young people and children, which has led to guidelines advising against prescription of SSRIs to those under the age of 18 in the UK 
- One study has provided some evidence to suggest that SSRIs are associated with an increased risk of suicidal behaviour in children and that most SSRIs seem to be ineffective for childhood depression. However the authors point out that further, longer term studies are required to assess the overall effect on population health of the recent rise in antidepressant use. 
- Another study failed to show any difference between different types of antidepressant medication and subsequent suicides. It did show, however, that suicide risk was highest in the early days of beginning to take any antidepressant, the authors felt that this was likely to be because people seeking help do so at the worst stages of their depression, and antidepressants are not immediately effective, so there is a higher risk in people who have been newly diagnosed and treated, compared with those who have been treated for some time. 
9. Other treatments
- In bipolar disorder, Lithium has been shown to be an effective treatment which lowers the risk of suicide. 
- Problem-solving therapy has been shown to help people who self-harm with depression, hopelessness and problems. As yet it has not been shown to reduce repeated self-harm. 
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