"We aimed to investigate the risk of substance use-related problems in ASD [autism spectrum disorder]."
Findings: "The risk of substance use-related problems was the highest among individuals with ASD and ADHD [attention-deficit hyperactivity disorder]."
So said the findings reported by Agnieszka Butwicka and colleagues  (open-access) looking again at an important but slightly uncomfortable topic: substance use-related problems or substance use disorder (SUD) with autism in mind. Covering various issues including those related to alcohol, drugs, tobacco, crime, somatic disease and death, authors "identified 26,986 probands with an autism spectrum disorders (ASD) among all individuals born in Sweden between January 1, 1973 and December 31, 2009" (yes, yet again it was one of those Scandinavian population registries that provided the data). Data from those diagnosed with autism or ASD were cross-referenced with information on substance-use related problems and compared with "unaffected (without an ASD diagnosis) full siblings (N = 30,456), half-siblings (N = 15,946), and parents (N = 50,155) of probands with ASD." Researchers also took into account issues such as comorbidity - "stratified on probands’ psychiatric comorbidity with ADHD" - and disposable family income and parental education. The examination of ADHD + autism continues an important research direction in recent times (see here).
Results: "Probands had a substantially increased risk of any substance-related problem..., such as substance use disorder..., somatic disease linked to alcohol misuse..., substance-related crime... and death." The sorts of statistics being produced with regards to 'risk' were not unimportant and indeed, were quite contrary to the 'stereotyped' view that "ASD patients are somehow protected from substance use-related problems" (authors words not mine). Further: "Within the substance use disorder category, the highest risk was found for drug use disorder..., followed by tobacco... and alcohol use disorder." The risk figures remained similar even when parental age, region of birth, education and family income were taken into account.
Insofar as one of the opening sentences of this post suggesting that autism + ADHD might be a particularly 'sensitive' combination when it comes to substance-use related problems, the data is pretty stark: "comorbid ADHD or ADHD with ID [intellectual disability] entailed a substantially higher risk, especially for substance use disorder." Autism + ID (without ADHD) however "was not associated with an increased risk of any substance use-related problems..., when all outcomes where regarded as one group."
I don't really want to go too far into the 'hows and whys' of the Butwicka data because this important area of investigation is still in it's infancy. I do appreciate the authors' discussions on how "substance use-related problems in individuals with ASD were indeed less common in the past, but that some factor(s) caused an increase over time" as being potentially important. They for example, talk about how "prior more narrow diagnostic practice may have [previously] excluded ASD patients with substance use-related issues or assigned other diagnoses to them." In other words, taking also into account how autism +ID did not seem to substantially increase the risk of substance use-related issues, the widening of the autism spectrum to potentially include more people might have had some effect on the relationship examined . Obviously, if true, this might have some important implications particularly when it comes to screening and also questioning what role substance use serves for this group in terms of reason(s) for starting and maintaining such behaviour(s).
The important autism + ADHD relationship also picked out by the authors is noteworthy. On several occasions on this blog I've discussed the cold, hard science that suggests that long-term outcome following a diagnosis of ADHD is not exactly brilliant when it comes to various individual and social variables (see here and see here for example). Without trying to generalise/stigmatise nor shift 'blame' from label to label, it's not outside the realms of possibility that comorbid ADHD diagnosis or even features of ADHD, might exert a significant influence on substance use behaviours  and the related problems stemming from their use. The implication is therefore, that efforts to minimise such adverse effects linked to a label of ADHD perhaps need to be stepped up.
It's always going to be difficult to talk about substance use disorder and the problems stemming from such behaviours with any specific diagnostic label in mind. There is a particular stigma attached to substance-use behaviours and certainly with autism in mind, more adverse sweeping generalisations are not required (see here for example). But this should not mean that discussions are buried and reality somehow airbrushed for the sake of political correctness or positive public relations. The reality as demonstrated by the Butwicka and other peer-reviewed data  is that substance use is / can be a destructive behaviour not least for the person and the people around them. Certainly in the context of autism and the quite large health and social disparities that seem to continually surround the diagnosis (see here for example), a failure to screen for and tackle substance use behaviours further adds to the adverse risks/inequalities that can potentially accompany a diagnosis.
 Butwicka A. et al. Increased Risk for Substance Use-Related Problems in Autism Spectrum Disorders: A Population-Based Cohort Study. J Autism Dev Disorder. 2016. Oct 12.
 Clarke T. et al. Substance use disorder in Asperger syndrome: An investigation into the development and maintenance of substance use disorder by individuals with a diagnosis of Asperger syndrome. Int J Drug Policy. 2016 Jan;27:154-63.
 Connolly RD. et al. Probabilities of ADD/ADHD and Related Substance Use Among Canadian Adults. J Atten Disord. 2016 May 14. pii: 1087054716647474.
 Arnevik EA. & Helverschou SB. Autism Spectrum Disorder and Co-occurring Substance Use Disorder - A Systematic Review. Subst Abuse. 2016 Aug 17;10:69-75.
Butwicka, A., Långström, N., Larsson, H., Lundström, S., Serlachius, E., Almqvist, C., Frisén, L., & Lichtenstein, P. (2016). Increased Risk for Substance Use-Related Problems in Autism Spectrum Disorders: A Population-Based Cohort Study Journal of Autism and Developmental Disorders DOI: 10.1007/s10803-016-2914-2