Obsessive-compulsive disorder (OCD) is a neurodevelopmental disorder affecting about 2% of the population whose symptoms frequently begin in childhood, although a formal diagnosis is often not made until adulthood1
. OCD is highly comorbid with many psychiatric disorders, including other anxiety, depressive, and tic disorders2–4
. However, its co-occurrence with attention-deficit hyperactivity disorder (ADHD), another common childhood-onset neurodevelopmental disorder that occurs in approximately 5% of the population, is less well understood5
. This relationship is of interest for several reasons: 1) both can present with symptoms of inattention and distraction, and differentiating between primary attentional symptoms and attentional symptoms secondary to a core anxiety disorder is important for prognosis and treatment6
, 2) OCD and ADHD are highly comorbid with Tourette Syndrome (TS)6
, each occurring in up to 50% of individuals with TS, suggesting that these three disorders may be etiologically related7–9
, and 3) family studies suggest that OCD and ADHD may co-segregate in families10–11
. Additionally, both ADHD and OCD are often missed or under-diagnosed, particularly during latency and early adolescence. Elucidating the relationship between these disorders will aid in appropriate diagnosis and treatment of these childhood-onset disorders, and will also advance our understanding their etiologies.
Reported prevalence rates of ADHD among individuals with OCD have varied widely, ranging from 0% to 51%12–13
. These discrepancies are likely due to study variation in method of data acquisition, sample size, age of participants, recruitment sources, and inclusion/exclusion criteria. For example, Jaisoorya et al. examined only individuals with adult-onset OCD (mean age at interview of 23 years), likely artificially reducing the rates of ADHD in their sample (0%) due to recall bias and waning ADHD symptoms in adolescence and early adulthood. In contrast, Geller et al. sampled from a pediatric OCD referral clinic, where approximately half of the participants were under 12 years of age; in this case, the tertiary care referral source may have led to higher rates of ADHD (51%) than would be seen in other samples. In addition to differences in the age of the study sample, the presence of other comorbid disorders, in particular tic disorders, may impact reported ADHD rates in OCD samples. As noted, both OCD and ADHD are highly comorbid with TS, a tic disorder that onsets in early childhood and has a prevalence of 0.5 to 1%9,14
. While some of the early studies of OCD/ADHD comorbidity excluded TS and other tic disorders, many of the more recent studies (those that found higher rates of ADHD) did not ().
Study characteristics and prevalence rates for studies examining ADHD rates in OCD participants.
Further, although the relationship between tics, OCD, and ADHD has been relatively well studied, the relationship between another syndrome that frequently overlaps with OCD, and has been postulated to be highly comorbid with ADHD, clinically significant hoarding behavior (hoarding), has been comparatively under-examined15
. Clinically significant hoarding is defined as the excessive acquisition of and unwillingness/inability to discard seemingly worthless items as they accumulate, leading to distress or impairment, including the inability to use work or living spaces for the purposes for which they were intended16–19
. Hoarding behaviors occur in a number of psychiatric disorders, including OCD, where prevalence estimates range from 18–40%20
Recent research suggests that problems with executive functioning commonly seen in ADHD may also occur in both OCD and non-OCD associated hoarding, including indecisiveness, disorganization, procrastination, slowness in completing tasks, actual or perceived alterations in memory, and difficulty with concentration and attention15,18,21–27
. However, only three studies to date have directly or indirectly examined the relationship between hoarding (ascertained without regard to OCD status) and ADHD ()15,22,28
. In the Hartl et al.15
study, hoarders reported higher rates of both inattentive and hyperactive ADHD symptoms and had higher rates of cognitive functioning deficits compared to non-hoarders. Although not directly assessing ADHD, Grisham et al22
also found that hoarders had more difficulty with sustained attention and increased impulsivity even when controlling for other clinically significant OCD symptoms, depression, and schizotypal symptoms, further suggesting an increased comorbidity between hoarding and ADHD22
Study characteristics for studies examining attentional symptoms in hoarding participants.
In contrast, Storch et al.28
found no difference in the rates of ADHD for hoarding compared to non-hoarding participants aged 7–17 with OCD28
. However, given that the age of onset for hoarding symptoms is around 13, with symptoms progressing in severity over time29–30
, and the high rates of ADHD in the sample (29% for hoarders vs. 24% for non-hoarders), it is possible that the rate of individuals who would develop hoarding, and thus the relationship between hoarding and ADHD, was artificially low28
Given the variation in reported prevalence rates of ADHD in the context of OCD, the relative lack of studies excluding comorbid tic disorders, and the potential relationship between hoarding and ADHD, the aim of this study was to examine the prevalence of DSM-IV ADHD as well as attentional symptoms in a sample of OCD participants with childhood onset of symptoms and without comorbid tic disorders, as well as to examine the relationship between hoarding and ADHD. We hypothesized that ADHD rates would be elevated in OCD without tics over that in the general population, but would be lower than seen in OCD with tics, and that individuals with hoarding would have more DSM-IV ADHD symptoms than individuals without hoarding.