ADHD and cannabis use

It is not uncommon for individuals to suffer from two or more psychiatric disorders at the same time. The appearance of these disorders frequently follows a specific order, and one disorder may predispose to others, all of which in combination contribute to the worsening of the quality of life of the individuals who suffer them. This is usually associated with more severe symptoms and worse prognosis. In addition, making a diagnosis and applying personalized treatments becomes more challenging in this context. By investigating the genetic overlap between disorders, we gain better understanding of why the disorders frequently co-occur.

In mental health, substance use disorders often appear when there is another mental condition. This is the case for attention-deficit/hyperactivity disorder (ADHD) and substance use disorder, where individuals with ADHD are more likely to use drugs during their lifetime than individuals who do not have ADHD. In particular, cannabis is the most commonly used substance among individuals with ADHD, which can also lead to the use of other drugs and to the worsening of their symptoms. ADHD is one of the most common neurodevelopmental disorders, affecting around 5% of children and 2.5% of adults, and is characterized by attention deficit, hyperactivity and impulsivity. Both ADHD and cannabis use are conditions determined partly by environmental factors but where genetic factors also play an important role.

We recently investigated the genetic overlap between ADHD and cannabis use, and found that the increased probability of using cannabis in individuals with ADHD, can be, in part, due to a common genetic background between the two conditions. We identified four genetic regions involved in increasing the risk of both ADHD and cannabis use, which could point to potential druggable targets and help to develop new treatments. In addition, we confirmed a causal link between ADHD and cannabis use, and estimated that individuals with ADHD are almost 8 times more likely to consume cannabis than those who do not have ADHD. This evidence goes in line with a temporal relationship, where the ADHD appears in childhood and the use of cannabis during adolescent or adulthood. This suggests that having ADHD increases the risk of using cannabis, and not vice versa.

This research has only been possible thanks to large international collaborations by the Psychiatric Genomics Consortium (PGC), iPSYCH, and the International Cannabis Consortium (ICC), where the genomes of around 85 000 individuals were analysed.

Overall, these results support the idea that psychiatric disorders are not independent, but have a common genetic background, and share biological pathways, which put some individuals at higher risk than others. This will help to overcome the stigma of addiction and mental disorders. In addition, the potential of using genetic information to identify individuals at higher risk will have a strong impact on prevention, early detection and treatment.

Further reading

María Soler Artigas et al. Attention-deficit/hyperactivity disorder and lifetime cannabis use: genetic overlap and causality, Molecular Psychiatry (2019) – https://www.nature.com/articles/s41380-018-0339-3

About the author

María Soler Artigas is postdoctoral researcher at the Psychiatry, Mental Health and Addictions group at Vall d’Hebron Institut de Recerca (VHIR), also part of the Biomedical Research Networking Center in Mental Health (CIBERSAM). Her research is part of the CoCA consortium that investigates comorbid conditions of ADHD.

Validation of DIVA 2.0: a new interview for diagnosis ADHD in adults

Despite the high prevalence of ADHD in adults, until recently, only the Conners Adult ADHD Diagnostic Interview for DSM-IV (CAADID) was the validated semi-structured interview available for the accurate diagnostic assessment of ADHD based on the DSM-IV criteria in the adult population. However, an important limitation of the CAADID that needs to be highlighted are the costs that come with its administration.

On the other hand, the DIVA 2.0 interview (Diagnostic Interview for ADHD in adults, DIVA 2.0, for its acronym in Dutch) is a semi-structured instrument which is freely available as a PDF on the website of the DIVA Foundation (www.divacenter.eu) and via a small one-off charge as a downloadable app. This semi-structured interview allows a thorough evaluation of the diagnostic criteria of DSM-IV-TR for ADHD in adulthood, as well as in childhood. It is divided into two domains, each applicable for childhood (before age 12) and for adulthood: the DSM-IV criteria for inattention, and for hyperactivity/impulsivity. The third part deals with the impairment caused by the ADHD symptoms in five areas of functioning (including work and education; relationships and family life; social contacts; free time and hobbies; self-confidence and self-image). For each criterion and age period, the DIVA 2.0 provides a list of specific and realistic examples of current or retrospective behaviors throughout life, that simplify the assessment of each of the 18 DSM-IV criteria required for the diagnosis of ADHD. The examples are based on common descriptions provided by the patients themselves. DIVA 2.0 also provides examples of the types of impairment commonly associated with the symptoms in five areas of daily life mentioned above. Whenever possible, the adult is interviewed in the presence of the partner or close relative who is familiar with the patient’s childhood, in order to evaluate simultaneously collateral and retrospective information (hetero-anamnesis).

This study investigates criterion and concurrent validity of the DIVA 2.0, a diagnostic semi-structured interview for ADHD in adults, based on the DSM-IV-TR criteria. Given that only one other study has investigated the validity of this interview, this is one of the first studies to carry forward the appropriate statistical analysis to explore the psychometric properties of the diagnostic tool in Spanish (Pettersson et al., 2015). Nevertheless, the study of Pettersson et al. compared DIVA 2.0 with an open clinical interview and in this study DIVA 2.0 was correlated with a semi-structured interview (CAADID).

The validation of this diagnostic interview provides us with an accurate and free diagnostic tool for assessing ADHD in the adult population, which can be useful in daily clinical practice and research settings. Findings from this piece of research provide support for the good reliability of this interview for the diagnosis of ADHD within the adult population. The findings demonstrate that DIVA 2.0 has a diagnostic accuracy for ADHD in adults of 100% when compared with the diagnosis obtained using the current gold standard diagnostic interview, the CAADID. Moreover, DIVA 2.0 appears to have similar psychometric properties as the CAADID as a diagnostic tool for adult ADHD. Regarding the validity of the interview, the results show a good correlation with the WURS scale when assessing ADHD symptoms for inattention, hyperactivity/impulsivity, and total symptoms during childhood. Along the same lines, fair results for concurrent validity were obtained for the assessment of symptoms during adulthood using the ADHD-Rating Scale and DIVA 2.0. Finally, a new updated DSM-5 version of DIVA is coming soon.

Complete abstract with link to pubmed and reference:

https://www.ncbi.nlm.nih.gov/pubmed/27125994