Each year in Australia one in five adults is thought to experience a mental illness (Australian Bureau of Statistics, 1997) and across the lifetime one in four will be affected by a mental disorder (World Health Organization, 2001). Given the mounting evidence that parental mental illness has a negative impact upon children (Reference Cantwell and BakerCantwell & Baker, 1984; Reference Beardslee, Versage and GladstoneBeardslee et al, 1998; Reference Klimes-Dougan, Free, Ronsaville, Stilwell, Welsh and Radke-YarrowKlimes-Dougan et al, 1999; Reference Mowbray and MowbrayMowbray & Mowbray, 2006; Reference Mowbray, Bybee, Oyserman, Marfarlane and BowersoxMowbray et al, 2006) and the clear need for early intervention and prevention in this area, it is surprising that prevalence estimates of numbers of children in families with a parental mental illness have not been forthcoming. With the growing emphasis on policy and programmes in this area (Reference James, Fraser and TalbotJames et al, 2007), this study sought to provide multiple estimates of the numbers of Victorian and Australian children living in families where a parent has a mental illness. Such estimates would provide important information to policy and programme developers.

Australian policy and planning

Currently, Australian policy and planning relies upon US data (Reference Nicholson, Biebel, Katzleavy, Williams, Manderscheid and HendersonNicholson et al, 2002) and/or small-scale Australian estimates extrapolated from adult in-patient mental health facilities (Reference Farrell, Handley, Hanke, Hazelton and JosephsFarrell et al, 1999; Reference Hearle, Plant, Jenner, Barkla and McGrathHearle et al, 1999; Reference Handley, Farrell, Josephs, Hanke and HazeltonHandley et al, 2001). In the USA, Nicholson et al (Reference Nicholson, Biebel, Katzleavy, Williams, Manderscheid and Henderson2002) found 68% of women and 54.5% of men with a non-substance psychiatric disorder slightly more likely to be parents than those without a psychiatric disorder (62.4% and 52.9% respectively). Unfortunately, this study focused on parents not children, did not differentiate between dependent and adult children and included single illness episodes across the life span, including those occurring before the children were born. For example, the parents’ average age at onset of psychiatric disorder was 4 years before their average age at the birth of the first child (Reference Nicholson, Biebel, Katzleavy, Williams, Manderscheid and HendersonNicholson et al, 2002). Nevertheless, this work was extremely important as it highlighted that US federal policies and programmes should explicitly acknowledge parenthood in mental illness, suggested that a large number of children were living in households where at least one of the parents had a mental illness and noted the feasibility of a large number of future policies and programmes for both parents and children (Reference Nicholson, Biebel, Katzleavy, Williams, Manderscheid and HendersonNicholson et al, 2002).

In Australia, several small-scale studies have made population estimates based on the proportion of service users with children undergoing treatment at a mental health facility (Reference Hearle, Plant, Jenner, Barkla and McGrathHearle et al, 1999; Reference Handley, Farrell, Josephs, Hanke and HazeltonHandley et al, 2001). The Australian Infant, Child, Adolescent and Family Mental Health Association (2001) summarised these estimates by suggesting that between 29 and 35% of adult mental health service users were women with children under the age of 18 years. This is a much lower estimate of parent status compared with that of Nicholson et al's (Reference Nicholson, Biebel, Katzleavy, Williams, Manderscheid and Henderson2002), although it should be noted that the Australian studies were based on small numbers of in-patients. Once again the number of children with parents who have had mental illness was not mentioned in the estimate.

Method

We used three methods to proffer multiple prevalence perspectives. First, we combined the Australian Bureau of Statistics (ABS) mental health studies (Australian Bureau of Statistics, 1997) with family characteristics studies (Australian Bureau of Statistics, 2003a ) to establish a population estimate. The second approach used records of all mental health service users in the state of Victoria during the 2003-2004 financial year. These service users are commonly considered to have a severely disabling mental illness (Victorian Mental Health Branch, personal communication, 2005 - one of the branch staff indicated that ‘the constitution of our clients is actually a mixture of “acute” and “chronic” cases’). The final approach used data from a moderately large general community survey of families with children 8-12 years old where parents self-identified their own and their spouse's mental health status (Reference Maybery, Reupert and GoodyearMaybery et al, 2006). We then extrapolated the data using ABS, Victorian and Australian population estimates (i.e. Victorian mental health attendees were extrapolated to the make Australian population estimates) to allow comparisons between the three approaches.

Results

The Australian Bureau of Statistics (1997) estimates that 12.5% of Australians experience a mental illness (excluding substance misuse-related mental illness and schizophrenia) during any 12-month period. Schizophrenia prevalence was included here based on estimates by Jablensky et al (Reference Jablensky, McGrath, Herrman, Castle, Gureje and Evans2000), subsequently raising the figure to 12.9%. In terms of family characteristics, as the likelihood of having a parent with a mental illness is doubled in children with two parents, separate calculations were undertaken for one- and two-parent Australian families (542 600 and 1967 000 families respectively) (Australian Bureau of Statistics, 2003a ). Two-parent families include the intact, step, blended and other classifications of families, as in the family characteristics report (Australian Bureau of Statistics, 2003a ). Similar calculations were undertaken for the state of Victoria. The combined families and children totals are shown in Table 1, along with the 23.28% prevalence ratio across the different family types.

Table 1. Australian and Victorian families and children living in families with at least one parent who has had a mental illness

		Australia, n			Victoria, n
Data source	Percentage of total population	Families	Children	Families	Children
12.9% ABS	23.3	577 507	1 082 403	142 326	266 397
20.4% VMH	1.3	32 254 1	59 325 2	7829	14 403
Cross-sectional study	14.4	361 382	668 462	88 214	163 267
Total	100.0	2 509 600	4 642 100	612 600	1 133 800

ABS, Australian Bureau of Statistics; VMH, Victorian Mental Health

1. Estimate based on VMH actual data

2. The ABS ratio (1.8743) of children: family was used to calculate the number of children for the VMH estimate

The data from the Victorian Mental Health Branch indicate that 7829 (20.4%) of the total 38 455 mental health service users for the year 2003-2004 were living with dependent children (Table 1; data were not available for the total number of children with parents with a mental illness and so do not include children not living with the parent). This is also extrapolated to the whole Australian population estimate.

Of the 701 parent participants in the community study, 83 responded (11.8%) that they had had a mental illness. In addition, 26 (3%) of participants responded that their spouse had had a mental illness. In total, in 101 (14.4%) of the families surveyed, at least one parent had a mental illness and a number of children had two parents with a mental illness. Although we recognise that in at least some families both parents would have a mental illness, such calculations were outside the scope of this paper.

Discussion

The three sets of data show different ‘snapshots’ of prevalence of children living in families with a parental mental illness. Multiple estimation allows triangulation of data from various sources. These diverse estimates make important additions to previous suggestions that approximately 30% of the Australian female mental health service users and 68% and 54% of US women and men with psychiatric disorders during their lifetime have dependent children (Australian Infant, Child, Adolescent and Family Mental Health Association, 2001; Reference Nicholson, Biebel, Katzleavy, Williams, Manderscheid and HendersonNicholson et al, 2002).

Importantly, we focused on numbers of children and families rather than only parenthood. Perhaps more important is the illustration of numbers from three diverse perspectives including a large-scale population estimate, actual mental health facility usage and a general community sample. Together, these different sources provide valuable planning information for government policy and interventions, as well as important information to community agencies regarding the issue of parental mental illness. The data about families and children in our study challenge psychiatric service providers to acknowledge the large number of children and families in their prevention, early intervention and mental health treatment policies.

Interestingly, there is a large divergence in estimates of the number of children in families with parental mental illness in the general population (23.3%; 1 million Australian and 250 000 Victorian) (Australian Bureau of Statistics, 2003a ) and in Victoria (1.3%; 60 000 estimated Australian and 14 403 Victorian) (Reference Maybery, Reupert and GoodyearMaybery et al, 2006). This can largely be explained by illness severity - all of the Victorian mental health service users could be considered to have a severely disabling mental illness compared with only 12.8% of those with a mental illness in Australia (the survey used multiple levels of illness disability; Australian Bureau of Statistics, 1997). Consequently, when illness severity is considered, the ABS estimate is much more comparable to the actual Victorian data. Together, these findings provide important information showing a broad picture estimate of all children in families with parental mental illness (i.e. 23.3% when not constrained by level of mental illness) and much smaller numbers (1.3%) where the illness is severe.

Unfortunately, although parental mental illness does not in itself guarantee poor outcomes for children, more severe parent disability has been associated with less sensitive and competent parenting (Reference Rogosch, Mowbray and BogatRogosch et al, 1992), significantly greater mental illness in offspring (Reference Warner, Mufson and WeissmanWarner et al, 1995), insecure infant attachment (Reference Teti, Gelfand, Messinger and RusselTeti et al, 1995; Reference Frankel and HarmonFrankel & Harmon, 1996) and lower quality of the mother-child relationship (Reference Harnish, Dodge and ValenteHarnish et al, 1995). The estimate of just under 60 000 children living with a parent with a severe mental illness in Australia is likely to be very accurate as the figures are extrapolated to the Australian context from the 14 403 children of Victorian parents with a severe mental illness. This suggests a large number of children likely to be at risk owing to their parents’ severe mental illness.

The third estimation of prevalence simply involved asking a general community sample of parents of children aged 8-12 years whether they or their partner had had a mental illness. The resulting prevalence of 14.4% was considerably lower than the 23.3% from the ABS study. The discrepancy might be partly explained by differences in survey methods (i.e. respondents replied to a single question regarding previous illness diagnosis, whereas the ABS used a diagnostic questionnaire to determine mental health status), but this still equates to 668 462 children and 163 267 families in Australia.