Introduction
EVIDENCE INDICATES that early interventions in a number of mental health conditions for children and young people can
result in better outcomes. Due to the high prevalence of mental health disorders in young people, every interaction or
consultation should be regarded as an opportunity to assess their psychosocial as well as physical wellbeing.
Prevalence and epidemiology of common mental health disorders in young people
in New Zealand
Mental disorders in young people are common
Around 20% of children and adolescents are estimated to have mental health disorders or problems, with similar types
of disorders being reported across cultures. About half of mental health disorders begin before the age of 14 years.
From a general practice perspective, many children will have important psychological problems at a subclinical level
which would benefit from intervention, and may be the precursors to adult disorders. These include behaviour and conduct
problems, significant school refusal and the excessively anxious child.
A 2006 epidemiological study in New Zealanders found the 12-month prevalence for major mental health disorders, in the
age band 16 to 24 years, to be 29% (Table 1).
| Table 1: New Zealand mental Health Survey: 12-month prevalence of any disorder and severity
by age. (Adapted from Oakley Browne 2006 2) |
| Age group (years) |
Twelve-month prevalence of any disorder (95% CI) |
Prevalence of serious disorder (95% CI) |
| 16–24 |
28.6 % (25.1, 32.3) |
7.2 % (5.7, 9.0) |
| 25–44 |
25.1 % (23.2, 27.1) |
5.8 % (5.0, 6.6) |
| 45–64 |
17.4 % (15.7,19.2) |
3.8 % (3.1, 4.5) |
| 65 and over |
7.1 % (5.7, 8.8) |
1.1 % (0.5, 2.0) |
Disorder includes: anxiety disorders, mood disorders, substance use disorders and eating disorders.
|
The most prevalent mental health disorders among young people in New Zealand are anxiety disorders, depression, conduct
disorder and substance abuse. The gender-specific prevalence of disorders varies with age, with an overall increase up
to the age of 18 years (Table 2). In childhood and early adolescence, males are at greater risk, with higher rates of
conduct disorder, attention-deficit hyperactivity disorder, and depressive disorder (depression and dysthymia). In adolescence,
the rates of depression/dysthymia and anxiety disorders increase dramatically in females, while the rate of substance
abuse is higher in males.1
| Table 2: Prevalence of common mental disorders in children and adolescents.1 |
Disorder (in order of prevalence)
|
Estimated population prevalence (%) |
| |
Total
|
Boys |
Girls |
| Preschool (also see box below) |
|
|
|
Preschool mental health problems (parent rated)
|
16 |
17 |
14 |
| Hyperactive behaviour disorder |
2 |
2 |
2 |
| Primary school age |
|
|
|
| Attention-deficit hyperactivity disorder |
14 |
19 |
9 |
Anxiety disorder (especially separation anxiety)
|
5 |
no data |
no data |
| Conduct disorder |
3 |
5 |
2 |
Depression/dysthymia
|
3 |
4 |
2 |
| Pre-adolescence (11 years) |
|
|
|
| Conduct/oppositional disorder |
9 |
12 |
5 |
| Attention-deficit hyperactivity disorder |
5 |
no data |
no data |
| Separation anxiety |
4 |
2 |
5 |
| Overanxious disorder |
3 |
4 |
2 |
| Depression/dysthymia |
2 |
3 |
<1 |
| Any mental disorder |
18 |
20 |
17 |
Mid-adolescence (15 years)
|
|
|
|
| Anxiety disorder |
13 |
7 |
19 |
| Conduct disorder |
5 |
7 |
3 |
| Depression/dysthymia |
6 |
3 |
9 |
| Any mental disorder |
22 |
16 |
18 |
Late adolescence (18 years)
|
|
|
|
| Alcohol or substance abuse/dependence |
24 |
29 |
20 |
| Depression/dysthymia |
18 |
10 |
27 |
| Anxiety disorder |
17 |
12 |
22 |
| Any mental disorder |
42 |
39 |
45 |
| NZ data have been used where available |
Childhood anxiety commonly precedes adolescent depression. In the presence of both anxiety and depression, there is
an increased risk of developing a comorbid substance use disorder and treatment responsiveness is reduced.1
Late puberty is commonly associated with experimentation with drugs (usually alcohol and marijuana) and also with a
three-fold increase in substance misuse. Multiple substance misuse is also common. Two-thirds of New Zealand adolescents
with marijuana dependence are also alcohol dependent. Clinicians tend to underestimate adolescent substance-related pathology
and this is probably the most commonly missed diagnosis in this age group.1
Mental disorders in young people lead to emotional distress, impaired functioning, physical ill-health and increased
suicide risk. They also carry a high risk of a pattern of recovery and recurrence (more likely in females) or unremitting
persistence (more likely in males) into adult life.1
Mental health problems in pre-school children and infants.
Some recent studies indicate that mental health problems are present in pre-school children and infants. A cohort study
carried out in Denmark reported a prevalence of mental health problems of 16 – 18% in children aged 1.5 years of
age. The most common problems were emotional, behavioural and eating disorders. Psychosocial problems and parent-child
disturbances appear to be risk factors for the development of a disorder in a very young child.3 In a recent
review the overall prevalence of disorders in children
aged 2 – 5 years was reported as about 16% with a similar spectrum of disorders to older children and adults.
The prevalence distribution within each disorder was different; for example, depression is more common in older children
and adults but oppositional defiant disorder (ODD) is more common in pre-schoolers.4
Common mental disorders often co-exist
Young people presenting with one disorder (e.g. depression) are at increased risk of having other disorders (e.g. substance
misuse or conduct disorder). Research conducted in New Zealand showed that 40% of 18 years olds who met the criteria for
a mental disorder had more than one disorder.1
New Zealand Suicide rates
Every year approximately 100 young New Zealanders (aged 15–24 years) die by suicide. This accounts for about a
fifth of the total number of suicides each year. While the rate of suicide for young people has declined by around 30%
since its peak in the late 1990’s, it continues to be a significant cause of death accounting for approximately
25% of all deaths in this age group.5
Men and Māori youth are particularly affected by suicide. Based on 2006 figures, young men have a rate of 31 per
100,000 population, which is significantly higher than the total population rate of 12 deaths per 100,000.5 The
Māori youth rate is 33 per 100,000 population compared with the non-Māori youth rate of 15 per 100,000.6
Suicide in children under the age of 10 is very rare, and uncommon in those aged 10–14 years.
International comparisons
New Zealand has one of the highest youth suicide rates among developed countries. This was highlighted in a 2009 WHO
publication7 which showed New Zealand teenagers (aged 15–19 years) had the highest rates of suicide in
the OECD for both men and women. Caution needs to be taken when making international comparisons of suicide rates because
many factors affect the recording and classification of suicide and can result in undercounting of suicide in other countries.
Key factors influencing reporting rates are the level of proof that is required for classification of a suicide, which
is very thorough in New Zealand and is made after a Coroner’s investigation. This means compared to other countries
New Zealand has a low number of “undetermined deaths”. The stigma associated with suicide may also influence
reporting rates as it deters the classification of a death as a suicide in some countries.
However, it is a significant concern that many young people die by suicide in this country and primary care needs to
be responsive to ensuring young people are provided with best practice assessment, treatment and management of suicide
risk and mental disorders.