Within the last 10 years increased research in child and adolescent neuropsychiatry could be recognized, but its value for and transfer into clinical practice is still under scrutiny. However, our knowledge about brain-behaviour relationship in child psychiatric disorders has grown tremendously and expectations of patients and healthcare providers are high to receive information with clinical relevance concerning better diagnostics, psychoeducation and treatment.

The JCPP has this in mind and the papers in this issue reflect the point raised for Attention Deficit-Hyperactivity Disorder, Tourette Syndrome and Autism Spectrum Disorders. Wiersema et al.’s aim was to test whether children with ADHD do not allocate the necessary extra effort in order to adjust their under-activated brain electrical state to the task in question. They suggest that deterioration of performance under slow event rate condition is associated with insufficient effort allocation and/or decreased motivation. This explains some of the daily behavioural problems of children with ADHD quite reasonably but shows also that, so far, there does not exist a technical tool that allows the clinician to disentangle whether children with ADHD are not able or not willing to invest extra effort; i.e. clinical experience and a broadband assessment procedure is demanded in these situations.

According to Banaschewski et al. this should include a visual examination that gives careful consideration to colour vision. The authors report the first time that in children with ADHD colour discrimination along the blue-yellow-axis (compared to red-green) is particularly impaired, indicating subtle problems in retinal dopaminergic mechanisms that are beyond the known alteration at dopaminergic brain synapses. It is suggested one should consider the colour of a stimulus when interpreting performance on a neuropsychological test in children with ADHD. Both studies support the view that children with ADHD do not only suffer from higher-order executive functioning deficits but also show problems at the level of sensory input and early information processing.

The annotation of Leckman et al. points to the likely role of aberrant neuronal oscillations in the pathogenesis of Tourette Syndrome (TS). Neural oscillations are periodic variations seen in the firing of neurons measured electrophysiologically, e.g. as frequency bands in the EEG. The latter reflect activity and cooperation of different brain networks. When the integration of these networks breaks down oscillations become dysrhythmic and disturbances of behaviour, cognition and emotion may develop. It is assumed that in TS a primary loss of basal ganglia control leads to thalamocortical dysrhythmia, while compensatory systems originating in the prefrontal cortex adaptively modulate the misguided striatal and thalamocortical oscillations. Repeated activation of these frontal systems can lead not only to tic suppression, but also to a wilful alteration of the character of movements involved. It is pointed that it is via these neural circuits that treatments such as Habit Reversal Training (HBT; a special behaviour therapeutic program) works in some cases of TS and that successful treatment of tics with neuroleptics as well as with deep electrical brain stimulation (for the severest cases only) can be explained by an anti-dysrhythmic effect on misguided neural oscillations. Leckman et al. explain their model and hypotheses in great detail to nurture future basic neurobiological research and treatment studies as well as a deeper understanding of the internal world of patients with TS.

Bloch et al. add to this a clinical developmental perspective of TS. Most parents want to know how their child's future with TS will be. So far, only a rough group-related answer can be given, which (in general) is positive, since most children with TS typically experience a significant decline in tic symptoms during adolescence. Bloch et al. identified an easily available clinical measure for fine motor-skill, the Purdue Pegboard Test (PPT), as predictive of adult tic severity and global psychosocial functioning. PPT may be used in combination with other indices to help predict outcome in children with TS.

Within the series of eight papers on Autism Spectrum Disorders (ASD; dealing with cognitive phenotype, social behaviour, sensory experiences, language impairment, joint attention and play intervention, early detection and restricted repetitive stereotypic behaviour (RRSB) the two on RRSB are especially interesting, since they investigated the latter issue systematically and moved the field forward from a neuropsychiatric view (Szatmari et al., Carcani-Rathwell et al.). RRSB is one of the three categorical criteria necessary for the diagnosis of ASD. The reported findings from both studies indicate that the RRSB domain is composed of two distinct dimensions: one of a ‘‘lower-order’’ (i.e. development of sensory-motor problems and repetitions), and another ‘‘higher-order’’ (i.e. restricted interest, ruminations, insistence of sameness/cognitive rigidity). Although both dimensions are present in ASD, the ‘‘higher-order’’ behaviour may be the more ‘‘autism specific’’ feature, while the ‘‘lower-order’’ behaviour is closer to mental retardation. If this is true it may not be appropriate to give equal weight to both in the diagnostic algorithms of ASD. Since the ‘‘higher-order’’ RRSB reflects merely obsessive-compulsive signs they may respond better to Selective-Serotonin-Reuptake-Inhibitors (SSRI) and behaviour therapy, while sensory-motor stereotypies are more difficult to treat and likely to be reduced by atypical neuroleptic drugs. This highlights the importance of deconstructing the RRSB domain during clinical assessment in order to better understand the behaviour of the child (as well as underlying altered specific neural networks) and more specifically target pharmacological and behavioural interventions.

In conclusion, this issue of JCPP clearly shows that brain-behaviour relationship in child psychiatric disorders is an important issue with clinical relevance, attractive for today's research groups. Either by investigating brain functions directly with the adequate instruments (e.g. EEG, fMRI) and interpreting what this tells us about clinical features or, the other way around, by using behavioural observation and neuropsychological testing, which might then be related to certain neuronal networks – it is always in mind to find better solutions for the treatment of patients.