Psychiatrists in Boston, Massachusetts, once thought they had the perfect way of encouraging families to join a programme aimed at tackling their emotional problems. Therapists hit the target neighbourhood with an attention-grabbing, rainbow-painted luxury trailer, brightly labelled as a mobile mental health unit - and wondered why the locals failed to climb aboard.
Dr Jacqueline Barnes of the Leopold Muller Centre at University College London, recounts this tale as an example of how early intervention programmes, no matter how well meaning, may founder.
Joint author of a Mental Health Foundation report called From pregnancy to early childhood; early interventions to enhance the mental health of children and families, Dr Barnes is certain that no single approach will have all the answers.
She says, 'For a while, it was considered bad to ask clients to come to clinics, and that services should be home-based instead. That's great if you like your home, but not if you have a violent partner, or your mother-in-law bursts in, or the telly's on, or the dog's there. And as in Boston, understandably, people would rather come in a taxi to the medical centre away from their neighbours. So you cannot presume that you know what is best.
In the UK, the obvious example of early intervention is the Government's Sure Start scheme, designed to address poverty and social exclusion by improving the health and well-being of families with young children.
Experts will be looking closely at an evaluation of that scheme for lessons on future implementations.
But the Mental Health Foundation believes that an answer must be found urgently to why so many parents (usually the most vulnerable) either will not participate, or simply drop out. Its newly launched project, Promoting Engagement, aims to find out why.
Statistics show that one in seven pre-school children experiences some kind of mental health problem. Evidence highlighted in the MHF's Bright Futures report in 1999 shows that early intervention programmes can be very effective in preventing this.
Dr Barnes' report confirms that early intervention programmes are most effective if they address at least two generations by including services for the child and for the parent.
Deborah Cornah, MHF consultant research manager, agrees there are multiple benefits. 'The evidence is that certain intervention can improve a child's behaviour, improve the mother's mental health, and improve relationships within the family, academic outcomes, cognitive skills and physical health.
'But we don't quite know the mechanisms of that. We don't know, for example, if mother's mental health improves because her child's behaviour improves, or vice versa.'
Dr Cornah is already aware of why some mothers do not accept the help of such programmes. They may question the intervention's relevance. 'Because a child is so closely identified with the mother, mothers are inherently moved to be defensive about their child's behaviour. They might say intervention is fine for children with difficult behaviour, but my child is fine, and intervention is not going to be any good for whatever reason. Or there are practical difficulties such as, who looks after my baby while I take my toddler to the hyperactivity clinic?'
The 15-month four-strand project started this spring in London, Southampton, Oxford and Flintshire, Wales, with families where children are at risk of or are showing early signs of developing mental health problems.
The sites were chosen to represent a wide cross-section of clients (rural, urban, affluent, economically deprived backgrounds), and types of intervention (post-natal, pre-school and school-age).
Professionals including psychiatrists, psychologists, health visitors and paediatricians will look at different age groups and different sorts of interventions - home-based (South-ampton), school-based (London), health visitors working with new mothers (Oxford), and an open clinic for parents and teachers (Wales).
Results, due in autumn 2003 and to be circulated to practitioners and policy-makers, should lead to a clearer understanding of the way forward.
They may well confirm what is already suggested by Dr Barnes' study. She and co-author Annemarie Freude-Lagevardi's surveys of practitioners including social workers, psychologists, psychotherapists, health visitors and child psychiatrists, came up with practical suggestions for good practice on how to engage hard-to-reach families.
These tips include conducting initial home assessments; using friendly persistence (follow-up calls, or a personal visit) for failed appointments and reluctant fathers; and noting down all available contact telephone numbers or addresses - teenage mothers, for example, may be based at various times either at their own home, with family and friends, or in a shelter.
Other strategies include establishing good, confidential relationships; avoiding frequent personnel changes; only promising what you can deliver; adopting a non-judgemental approach; and being culturally sensitive.
There are plenty of ways of making intervention seem more attractive - rewarding participants (gift vouchers, free transport); having flexible time-tables; setting up home visits; and arranging childcare, meals, a comfortable environment or other useful services like laundry, a toy bank, or clothes exchange. Another way is being prepared to offer crisis intervention to overcome housing or financial difficulties before addressing other parenting issues.
These ideas may seem obvious, perhaps, but they are by no means universally adopted. Dr Barnes says, 'You almost feel ashamed presenting these strategies within the document because they are so self-evident - and yet they are not done.'
One of the recommendations in her report is that there should be much more co-ordination between the voluntary sector and higher levels of mental health services. Dr Barnes says, 'It's always the middle class ones who get their psychotherapy, because they know how to set about getting that, whereas the most vulnerable people who are in real distress think, I already have too much wrong in my life, I cannot cope with this too.
'I expect the Promoting Engagement research will confirm what is becoming evident - that you cannot be as prescriptive as in the past.'