Autistic spectrum disorder (ASD) is a modern enigma. The “triad of impairments” summarises the potentially devastating effects of ASD in social understanding and relationships, attention and communication, flexibility of thinking and behaviour.

While researchers largely agree that people with ASD have different neurological “wiring”, we have no idea how this comes about. There is likely to be an inherited component, but we do not know how genetic vulnerability interacts with other environmental factors. Hence, the ASD field is rife with speculation, scaremongering and misplaced evangelism, especially when it comes to intervention.

Researchers have been preoccupied with outcomes of treatment for ASD, comparing one method with another for effectiveness, asking the “big” but wrong question. To design better interventions for the future we must find out the small detail of why certain treatment components work for which children and families, in what circumstances.

Instead of “which method works best?”, we should ask “what strategy is helpful or unhelpful for what problem?”. Almost no attention has been given to families’ experience of intervention and whether this brought added stress.

At Bristol university we recently completed a four-year study involving 50 families (south west autism programme or SWAP). Funded by Bristol city council, SWAP investigated how education authorities can best provide early intervention, drawing on a range of options, including behavioural psychology and speech therapy. Rather than imposing a preferred approach, intervention was tailored to the resources and needs of each family. For any method it is important to ask questions of the underlying theory, the evidence base for success, and to listen to what parents say about the practical, emotional, and financial costs involved.

Several families in our study had previously embarked on their own “high dosage” behavioural programmes, aided by pressure groups and bought-in “consultants”. Applied Behavioural Analysis (or ABA) views ASD in terms of learned excesses and deficits. Through intensive drills, new behaviours are broken down into small steps, taught, prompted and rewarded, for example, by praise, hugs or food.

In the Lovaas version of ABA developed in Los Angeles, children who made most progress were given 1:1 training for 40 hours a week, 52 weeks a year, leading to claims of “recovery” from ASD in some cases. Much criticism has been levelled at the experimental evidence supporting this work and the difficulty of generalising from the tightly controlled conditions of a laboratory into homes and schools, although undoubtedly many children benefit from the high levels of structure involved. Where an LEA makes no provision for ASD, parents will fight through the courts, with lawyers holding out for ABA intervention at pound;25, 000 plus per child per year.

But the biggest costs are borne by the families: in the Bristol study the stresses on siblings and family life of “going it alone” to implement ABA were inestimable, and not all children made progress. Given that a main aim in ASD intervention is to promote children’s spontaneity and flexibility, there are concerns about any method based on drills. When SWAP offered direct input to families, the average take-up was 10 hours per week, no family opted exclusively for ABA, and while all made dramatic progress, children who made greatest gains were not those who received the most time.

In contrast, TEACCH (Treatment and Education of Autistic and Related Communication Handicapped Children) views ASD as a distinct “culture” or way of processing the world, which you can modify but not recover from.

Developed in North Carolina, this approach has been adopted by many specialist schools and units in the UK, including SWAP, with a focus on utilising the strengths of children with ASD, such as their strong visual sense and preference for consistency, systems and order.

The breakthrough for many families is when children with ASD begin to signal needs and intentions, when they see the point of acting on the world to produce change. Many parents in SWAP attended the EarlyBird three-month programmes developed by the National Autistic Society, which use home visits, video-feedback and support groups to promote practical strategies, especially in social interaction. Parents are taught how to observe, to follow a child’s interest and analyse underlying triggers and functions of inappropriate behaviour.

A method used in EarlyBird and SWAP to foster communication is PECS (picture exchange communication system), which uses symbols.

Many parents of children with ASD have concerns about diet. Various “metabolic” theories have been put forward: that ASD is caused by vitamin deficiencies, excessive intestinal yeast, or gluten and casein intolerance.

Some parents in SWAP found that avoiding sugar, caffeine, cereals and milk helped.

An intensive 1:1 play approach that incorporates dietary regimes is Options (Son-Rise), developed in Massachusetts and based on acceptance and approval of ASD behaviour. Non-distracting environments are created with light filters on windows, neutral colours and no noise distractions. Here adults simplify language, follow the child’s lead and focus on interaction, especially eye contact. Although some UK schools have adopted parts of Options, there are tensions in not setting clear objectives and restricting the child’s experience.

In searching to crack the ASD enigma, some speculators have built explanations around distortions in sound sensitivity (auditory integration training), while Japanese daily life therapy emphasises movement and rhythm in exercise and daily PE.

For parents and teachers looking at what to do for the best, hope and reality are in fine balance. Zealots apart, the NAS and DfES autism working group have got it right when they recommend a range of interventions to meet a range of needs.

Alec Webster is professor of education at Bristol university

* For LEAs to do nothing is not an option.

* Put children and families first and tailor strategies to their individual needs.

* Recognise the stresses in coping with ASD and following an intervention programme.

* Accept there are no guarantees attached to any method.

* Be eclectic and draw on different strategies.

* Hand over strategies to parents to promote self-help.

* Take note of what works, for whom, and in what context, since this is the key to the future.