Abstract
Obsessive compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD) are two of the most common neuropsychiatric diseases in paediatric populations. The high comorbidity of ADHD and OCD with each other, especially of ADHD in paediatric OCD, is well described. OCD and ADHD often follow a chronic course with persistent rates of at least 40–50 %. Family studies showed high heritability in ADHD and OCD, and some genetic findings showed similar variants for both disorders of the same pathogenetic mechanisms, whereas other genetic findings may differentiate between ADHD and OCD. Neuropsychological and neuroimaging studies suggest that partly similar executive functions are affected in both disorders. The deficits in the corresponding brain networks may be responsible for the perseverative, compulsive symptoms in OCD but also for the disinhibited and impulsive symptoms characterizing ADHD. This article reviews the current literature of neuroimaging, neurochemical circuitry, neuropsychological and genetic findings considering similarities as well as differences between OCD and ADHD.
Highlights
Obsessive compulsive disorders (OCD) are typically characterized by the presence of recurrent, intrusive, and disturbing thoughts which often elicit anxiety or emotional stress followed by repetitive stereotypic behaviour or thoughts in order to neutralize the negative affects (American Psychiatric Association 1994)
According to many association studies followed by meta-analysis, it has been shown that the 10-repeat allele of the DAT1 is a risk allele for attention deficit hyperactivity disorder (ADHD) in childhood (Gizer et al 2009; Table 2), while persistent ADHD in adults was associated with the 9-repeat allele (Franke et al 2010), findings that might point to a regulatory effect of dopamine transporter (DAT) in brain development
In the case of OCD, they could be caused by the overflow of intrusive thoughts, whereas in ADHD, it might be due to a lack of inhibitory control and to an impulsive response style
Summary
Obsessive compulsive disorders (OCD) are typically characterized by the presence of recurrent, intrusive, and disturbing thoughts (obsessions) which often elicit anxiety or emotional stress followed by repetitive stereotypic behaviour or thoughts (compulsions) in order to neutralize the negative affects (American Psychiatric Association 1994). According to DSM-5 criteria, ADHD is classified as a neurodevelopmental disorder, which is a group of conditions with onset in the developmental period These disorders ( including autism spectrum disorders and learning disorders) typically manifest in early development, often before the child enters grade school, and are characterized by developmental deficits that produce impairments of a broad range of social functioning (American Psychiatric Association 2013). A study concerning the relationship between OCD and ADHD in children and adolescents using familial risk analysis provided further evidence of a familial relationship, in addition to unique aetiological factors for both OCD and ADHD (Geller et al 2007a, b) This is of special importance because of the high comorbidity for both OCD and ADHD disorders. The aim of this overview is to help to understand the aetiology of psychiatric disorders, in particular concerning ADHD and OCD
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