Projects

About 32% of adolescents with ADHD report cannabis use, and about 12% meet the criteria for cannabis use disorder (CUD). This association leads to higher rates of psychiatric comorbidities, more severe substance use disorders, poorer treatment outcomes and lower quality of life. Individuals with ADHD are almost three times more likely to receive a CUD diagnosis than the general population. A Mendelian randomization study found even higher odds ratios for this association at the genetic level. Both disorders appear to partially involve common neural circuits underlying executive functions, impulsivity, cognitive control and reward response.

First-line therapies for ADHD generally do not show efficacy in reducing cannabis use. At the same time, behavioral and psychosocial interventions for CUD are not always effective or well tolerated. New approaches targeting craving are needed as it is the leading cause of relapse in comorbid ADHD and CUD. Neuromodulation such as transcranial direct current stimulation (tDCS) has been shown to be effective for substance use disorders, with a high degree of tolerability and safety and no risk of abuse.

A planned study (B. Rubio, L. Smigielski, S. Walitza) will investigate whether 10 sessions of anodal stimulation of the right dorsolateral prefrontal cortex and cathodal stimulation of the left dorsolateral prefrontal cortex (2 mA, 10 x 20 minutes) can reduce craving, cannabis use and ADHD symptoms. The study design is randomized, double-blind, sham-controlled and interventional with n = 36 subjects. Endpoints include the Marijuana Craving Questionnaire (MCQ), urinary cannabis concentration, Conners ADHD Rating Scale, EEG theta and delta tapes, and neuropsychological tests of inhibition and risk taking.

This study aims to fill a gap in the treatment of comorbid ADHD and CUD by testing innovative neuromodulation techniques to improve inhibitory control.

Excessive risk-taking, impulsivity and sensation-seeking are often an expression of psychiatric disorders, especially ADHD. ADHD is the most common neurodevelopmental disorder in childhood and often continues into adulthood. Recent studies confirm the common genetic basis of ADHD and at-risk behavior, but the exact mechanisms behind it are unclear. This gap in knowledge exists despite the individual and societal consequences of risky behavior, which often manifest themselves in the form of substance abuse, reckless driving or delinquency. Probably in no other area is the intrinsic risk factor as obvious as in extreme sports, which can lead to serious injury or death and pose a challenge for emergency medicine.

In the currently implemented study (L. Smigielski, S. Walitza, S. Brem, A. Buadze), ADHD patients, extreme athletes and control groups will be examined. The study will decompose the risk behavior phenotype into five neurocognitive domains (risk taking, decision making, response inhibition, threat stimulus and cognitive processing of preventive messages), which will be tested in five brain imaging experiments. These experiments are drawn from neuroeconomic risk-return paradigms, affective threat exposure, impulsivity research, and consumer neuroscience. In addition, white matter microstructure and genetic data will be collected and analyzed.

This study will help to understand, in the language of cognitive neuroscience, why certain individuals engage in dangerous activities. It will explore the interactions between the striatum (reward), amygdala (threat) and prefrontal cortex (cognitive control) that may inspire new strategies for "unlearning" these mechanisms. It will provide clues for therapeutic interventions for ADHD and prevention and harm minimization strategies for extreme risk taking. Since avoidance behavior is the main feature of anxiety, understanding low anxiety may also provide insights into the development and maintenance of anxiety disorders.

What is this study about?
The Child and Adolescent Psychiatric Service of the Canton of Zurich is currently offering affected children and adolescents between the ages of 6 and 17 the opportunity to take part in an observational study on the drug treatment of ADHD. The study is investigating the long-term tolerability of methylphenidate (e.g. CONCERTA®, Equasym®, Equasym® Retard, Medikinet®, Medikinet® Retard, Ritalin® and Ritalin® LA). Several clinics throughout Germany and other European countries are also involved in conducting this study.