There is a danger that psychiatrists who treat adults may continue to believe that life begins at the age of 18, and ignore mental disorders suffered by children. The same is true of the general public. But about two thirds of those who have depression in childhood will have a further episode when they grow up. Childhood psychiatric illnesses, which affect around 13 per cent of children, often go undiagnosed and untreated.
Depression in children can be diagnosed as early as six or even younger, though it is often associated with other disorders such as attention deficit and general disruptive behaviour. The symptoms are similar to those seen in adults inability to sleep, a low mood, negativity, feelings of worthlessness and often physical symptoms like stomach ache. Young children rarely have suicidal thoughts, but adolescents often do and theydo make suicidal attempts.
The incidence of depression in young children prior to puberty is around one in 50. This increases to around two in 50 adolescents. In younger children, the incidence is the same in girls and boys; in adolescents, the incidence in girls is about double that in boys.
The earlier puberty occurs in girls, the greater the chance of a depressive episode. This is probably related to hormonal changes. The incidence of depression in adult women worldwide is twice that of men.
Children of depressed parents have a three-fold higher risk of depression, reflecting genetic factors and parental behaviour. Studies on identical and non-identical twins show that about half of the vulnerability to depression is genetic.
Specific abnormalities in the development of the brain may predispose a child to depression. One such structure is the amygdala, which plays a key role in emotional responses. In another region, the prefrontal cortex, there is a reduction in brain cells. There is also increasing evidence that abnormalities in chemical factors, sex hormones and growth hormones may be both predictors and causes of a future episode.
Life events involving a loss of some sort can trigger depression, so it is not surprising that child abuse, physical or sexual, is a major factor. Dysfunctional family relationships also play a role. One study showed that the parents who had been involved in crime had a huge impact on the probability of their young children becoming depressed.
The condition can be successfully treated both by drugs and psychotherapy. In severe cases, antidepressants are thought to work by increasing the levels of serotonin, a chemical transmitter in the brain. The older antidepressants tricyclics do not seem to work on prepubertal children. Cognitive behavioural or interpersonal psychotherapy, which deal directly with the child's conscious thoughts and problems, can have positive results. Providing information about the illness to the family, and the child, can be invaluable.
Depression can disrupt family life and often has a very serious impact on children, even when they recover. A child has described a depressive episode as having his existence put into parenthesis: a period of his life was lost forever.
Lewis Wolpert is professor of biology as applied to medicine at University College, London