With the recent legalization of cannabis in certain jurisdictions (e.g., Canada, Mexico, Thailand, parts of the United States and Australia, amongst others), empirical research into the effects of acute and chronic cannabis use is needed. Heavy cannabis use is associated with more frequent and distressing positive symptoms of psychosis such as hallucinations and delusions in both clinical (Hasan et al., 2020, Quattrone et al., 2021) and nonclinical samples (Quattrone et al., 2017, Ragazzi et al., 2018). Research supports a continuum of psychotic experiences from subthreshold to the clinical threshold of SSDs (Ermel et al., 2019) and further suggest that we may observe cognitive impairments associated with SSDs on a similar continuum (Barkus et al., 2005, DeRosse and Karlsgodt, 2015).

Given the robust literature demonstrating lower executive functioning performance associated with cannabis use (Ross et al., 2020), SSDs (Orellana & Slachevsky, 2013), and PLEs (O’Brien et al., 2020, Wolf et al., 2015), as well as the neuropathophysiological overlap underlying these conditions (e.g., dysfunction of the prefrontal cortex [PFC]; Chambers et al., 2001; Solowij & Michie, 2007), additive effects of cannabis use on deficits in executive functioning have been hypothesized in people with SSDs (Whitfield-Gabrieli et al., 2018). However, findings are often mixed, which are thought to reflect several potential confounds related to medication, nicotine use, and social-functioning constraints on drug access (Løberg and Hugdahl, 2009, Núñez et al., 2016, Sabe et al., 2020, Volk and Lewis, 2016). As many of these confounds may not be present to the same extent in nonclinical samples who present with a range of cannabis use and PLEs, they may offer sensitivity to study the potential additive effects of cannabis use and psychotic symptoms on executive functioning. Moreover, further understanding of cannabis use and subclinical psychotic symptoms may be informative to the complicated relationship between cannabis use and psychotic disorders. Yet, to our knowledge, the current study is the first to investigate executive functioning in relation to problematic cannabis use amongst people who endorse PLEs.

As a result of aberrant functioning in the PFC, dysregulation of pyramidal neurons, and disrupted neurotransmitter signaling, individuals with SSDs experience deficits in executive functioning, including working memory, sustained attention, goal-oriented planning, and inhibition (Orellana & Slachevsky, 2013). For example, two well-established tasks of executive functioning associated with PFC integrity that have been widely studied in this sample are the Wisconsin Card Sorting Task (WCST; Asgharian Asl & Vaghef, 2022; Lombardi et al., 1999) and the Iowa Gambling Task (Kobayakawa et al., 2017, Ouerchefani et al., 2019, Zha et al., 2022). Studies have consistently demonstrated that people with SSDs exhibit impaired performance on the WCST (particularly perseveration; Everett et al., 2001; Sullivan et al., 1993), indicating poor set shifting and cognitive flexibility. Furthermore, people with SSDs have poor performance on the IGT (Beninger et al., 2003, Ritter et al., 2004, Shurman et al., 2005), indicating risky decision making. Thus, given existing dysregulated functioning of pyramidal neurons in the PFC (Volk & Lewis, 2016) that modulate executive functions, it is suggested that people with SSDs may be more vulnerable than people without SSDs to neurotoxic effects of cannabis (Rabin et al., 2014), as cannabis disrupts endocannabinoid-mediated neurocognitive systems (Volk & Lewis, 2016).

Similarly, a range of studies across various brain systems implicated in SSDs suggest a continuum of cognitive functioning underlies subclinical and clinical psychosis phenomena (Ettinger et al., 2012, Garrity et al., 2007, Orr et al., 2014, Sheffield et al., 2016, Van Dellen et al., 2016), which may indicate a similar neurobiological vulnerability to cannabis use in people with PLEs. Sabaroedin and colleagues (2019), for instance, found reduced functional connectivity between the dorsal striatum and PFC correlated with more severe positive PLEs in a sample from the general population. Reduced right dorsolateral PFC activity in youth with positive PLEs has also been observed during Go-No Go (Bourque et al. 2017a), working memory (O’Brien et al., 2020, Wolf et al., 2015), and response inhibition tasks (Jacobson et al., 2010). Thus, people who endorse frequent and distressing positive PLEs may also experience PFC-mediated executive dysfunction, and thus may be more vulnerable to neurotoxic effects of cannabis, similar to those with SSDs.

Problematic cannabis use is also associated with aberrance of the PFC, specifically dorsolateral (Hermann et al., 2007) and orbital frontal regions (OFC; Lorenzetti et al., 2019), which is reflected in impaired performance on the WCST (Fontes et al., 2011) and IGT (Bolla et al., 2005). Thus, we may expect to see additive effects of cannabis use on deficits in these tasks in people with SSDs. However, there are some counterintuitive findings in studies assessing relations between frequency and amount of cannabis consumption with cognitive functioning in this population. For example, while some studies have found that a history of cannabis use among individuals with first episode psychosis is associated with worse performance on tasks assessing executive functioning, verbal memory, and global cognition (González-Pinto et al., 2016, Mata et al., 2008), other studies report better attentional and executive functioning in those with first episode psychosis who report lifetime cannabis use compared to those who do not (Cunha et al., 2013). Moreover, another study found that both low and high frequency cannabis use were strongly associated with impairments on a range of cognitive tasks in SSDs, whereas moderate use was not (Schnakenberg Martin et al., 2016). As noted above, a number of confounding factors may affect this relationship including cognitive functioning, complex neuropathophysiology of SSDs, medication, and the cognitive-enhancing effects of nicotine use (Núñez et al., 2016, Sabe et al., 2020, Volk and Lewis, 2016). Given these complexities in the clinical SSD literature, it may be fruitful to investigate the relations between cannabis use and cognition in nonclinical samples with PLEs.

Heavier cannabis use in individuals who endorse PLEs is associated with positive and negative symptoms of psychosis that are of greater severity, and may be more distressing and frequent (Kelleher et al., 2015, Ragazzi et al., 2018). Notably, more frequent and distressing positive symptoms of psychosis relate to greater impairments in certain executive functions, which some suggest may be due to distress or distraction (Barnes et al., 2021, Hegelstad et al., 2020, Ziermans, 2013). Furthermore, individuals with PLEs may have underlying PFC dysfunction that exists on a continuum with SSDs (Ettinger et al., 2012, Garrity et al., 2007, Orr et al., 2014, Sheffield et al., 2016, Van Dellen et al., 2016), potentially increasing vulnerability to neurotoxic effects of cannabis. Thus, individuals who experience frequent and distressing PLEs and engage in problematic cannabis use may experience greater impairments in executive functioning performance.

Accordingly, we hypothesized that individuals with problematic cannabis use patterns are more likely to experience executive functioning deficits if they endorse high positive PLEs, specifically regarding decision-making on the IGT and perseverative errors assessed by performance on a Card Sorting Task (CST). The IGT has demonstrated sensitivity to detecting deficits in nonclinical samples using cannabis (Whitlow et al., 2004). This task relies on intact risk assessment and decision making and assesses higher order executive functioning (Kobayakawa et al., 2017). In addition, CSTs assess higher-order executive functioning, and have revealed deficits in both nonclinical (Pope & Yurgelun-Todd, 1996) and clinical samples (Rabin et al., 2013) that use cannabis. The task relies on intact attention, cognitive flexibility, working memory, and visual processing (Haywood & Baughman, 2021). Given the potential confound of nicotine co-use noted above, we also covary for problematic nicotine and other drug use.