Hello Jo, I'm an ex mental health nurse with 3 grown up boys in our familly. One had a behavioural reaction to milk products at 10 months old, when he switched from a diet of breat and soya milk to cows milk.(we were awake every night for weeks, and when we eliminated the cows milk, his behaviour reverted straight back to laid back!) I have a friend who rarely ever gave her daughter sweets with colouring and one day, aged 5, she'd been given an ice-lolly by a relative. Within minutes the girl was lierally banging her head against the car roof and screaming blue murder. She had to be restrained to prevent her from hurting herself. The hospital said it was a reaction to the addditives and most likely the colouring. There are several books and thousands of studies about E numbers, many of which are not still banned.
I specialised in adult behavioural disorders, so although no direct experience at work, with ADHD in children, was often in contact with teams working in the field. The way I've been taught to understand ADHD is that it's merely an identifying label given to a set of behavioural symptoms. ADHD was "invented and not discovered." "ADHD" is useful as shorthand,when you're trying to describe how someone behaves, but not useful to the person, nor to the actual process of treatment as it results in discrimination in the wrong hands and gives the impression of an immovable state of being that is rather like a learning disability. So it's not like a having cold or like being diabetic.
As the causes are unknown specifically, they are very likely to be a mixture of causes, so, for example, your child may have had reactions to foods as a baby/toddler and has developed a strategy of seeking attention which you and close contacts, have become conditioned to accept and encourage. Carers need to experiment in order to discover what is triggering this behaviour and it's not easy.
Health professionals in our services usually attributed it to either food reactions, or behavioural strategies to get attention which have developed unchecked. Or, more often the case , BOTH. Doctors tended to prescribe medications, and nurses and psychologists prescribed experimenting with food and behavioural techniques.
A very good book I read used the basic concept of 3 steps 1/ignoring bad behaviour as the core aim, 2/ reasonable and consistent punishment for dangerous seriously bad behaviour (so yes, reactiong, but only in a consistently reasonable way appropriate to the level of behaviour) and 3/consistent reasonable rewards for good behaviour in the form of extra attention. This approach works very well with adults too and is used in very difficult entrenched cases of self harming and personality disorders( the aim for them is to achieve a sense of responsibililty for their actions).
So, for me as a parent and nurse not reacting AT ALL to behaviours that are irritating I always find the most difficult challenge, because if someone irritates me I ALWAYS want to tell them to stop. It remains a challenge. But I guarantee it works, if you can stick to it.
Going back to the ADHD specifically, wikipedia is a good source of scientific references and says this about treatments effectiveness "Methods of treatment often involve some combination of behavior modification, life-style changes, counseling, and medication. A 2005 study found that medical management and behavioral treatment is the most effective ADHD management strategy, followed by medication alone, and then behavioral treatment.[107] While medication has been shown to improve behavior when taken over the short term, they have not been shown to alter long-term outcomes.[108] Medications have at least some effect in about 80% of people.[109] Dietary modifications may also be of benefit.[110]"
I personally really think food and additives and behaviour are the best starting points and if it's too hard to cope with, add medication to the startegy. Not forgetting that medication should be seen as a SHORT TERM addition to the behavioural and physical changes in diet.