Obsessive-compulsive disorder (OCD) has a lifetime prevalence of close to three percent
and is one of the leading causes of disability worldwide. In addition to being associated
with significant functional impairment in daily living and quality of life, OCD has been
associated with neurocognitive deficits. Meta-analyses have found that individuals with
OCD tend to perform worse on measures of neurocognitive functioning, including aspects of
memory and executive functioning, compared to healthy controls, and that symptom severity
is associated with worse cognitive functioning. While effective treatments for symptoms
of OCD have consistently been identified, research findings regarding the impact of these
treatments on cognitive functions related to OCD have been mixed. In addition, cognitive
behavioural therapy (CBT), which incorporates exposure/response prevention (ERP) and
cognitive therapy, is considered the gold-standard treatment for OCD. However, a
substantial proportion of clients fail to respond to the treatment, and the majority of
treatment responders still continue to report impairing levels of symptoms. A possible
novel therapeutic approach is the use of repetitive transcranial magnetic stimulation
(rTMS), a non-invasive procedure that uses electromagnetic field pulses to stimulate
regions of the brain. rTMS can induce excitatory and inhibitory neural activity in the
neural circuits of the motor cortex. In OCD, rTMS has shown a moderate therapeutic effect
on obsessive-compulsive disorder symptom severity with response rates surpassing those of
sham conditions, and has shown to lead to significant improvements in cognitive functions
such as working memory, executive functioning, and attention. There is emergent empirical
literature supporting the synergistic effects of rTMS with CBT in a range of psychiatric
conditions although this has yet to be tested directly in OCD.
The proposed study aims to provide a pilot, proof of principle test of the clinical
efficacy and treatment mechanisms of adding brief rTMS prior to completing CBT for OCD
for patient participants with DSM-5 diagnosed OCD. It also aims to provide a preliminary
examination of the extent to which rTMS leads to neuropsychological improvement and the
extent to which cognitive improvement relates to improved CBT treatment response. The
primary goals are to compare the relative efficacy of rTMS plus CBT to CBT alone at
reducing OCD symptoms, and to examine the extent to which neuropsychological change on
measures of attention, memory, and executive functioning during rTMS relate to subsequent
treatment success with CBT. Treatment outcomes will be assessed using standardized
measures of OCD symptoms, as well as measures of mood, anxiety, and wellbeing. If this
pilot study can demonstrate that a brief rTMS intervention of 10 sessions over a two-week
period can confer significant clinical gains for those suffering with OCD through
neuropsychological improvement and that these improvements, in turn, can enhance the
effectiveness of CBT, then it could easily be translated into highly accessible, routine
clinical care. Further, demonstration of improvement in OCD-associated neurophysiological
dysfunction, given the refractory nature of the illness, would provide another avenue
into the long-term enhancement of outcomes for this chronically affected population.
Results will also add to our understanding of the role of psychological mechanisms in the
pathogenesis and treatment response in OCD.