The primary noneuphorizing and nonaddictive compound of cannabis, cannabidiol (CBD), has recently been shown to possess considerable therapeutic potential for treating a wide range of neuropsychiatric disorders (De Gregorio et al., 2019). They include chronic pain (Costa et al., 2007), nausea (Parker et al., 2006), epilepsy (Devinsky et al., 2016), psychosis (McGuire et al., 2018), and anxiety (Scuderi et al., 2009; Whiting et al., 2015). CBD in therapeutics is used within a large therapeutic window, which ranges from 2.85 to 50 mg/kg/day (Whiting et al., 2015; Devinsky et al., 2016). While this fact indicates that its therapeutic dose is still mostly unknown, clinical studies have revealed that CBD could produce analgesic and anxiolytic effects exerted through its interaction with 5HT1A receptors (De Gregorio et al., 2019). As a potential anxiolytic treatment, in particular, it has drawn increasing interest. A review (Blessing et al., 2015) concluded that existing preclinical evidence strongly supports CBD as a treatment for generalized anxiety disorder, panic disorder, obsessive-compulsive disorder, and posttraumatic disorder when administered acutely.

Clinical data showing therapeutic effects of CBD in patients with anxiety disorders, however, are still meager (Bergamaschi et al., 2011; Crippa et al., 2011). The purpose of the present study was to investigate these effects in patients with social anxiety disorder (SAD).

SAD is characterized by excessive anxiety in situations where a person might feel judged, such as performance situations, and situations involving interpersonal contact with others (American Psychiatric Association, 2000). This is the fear of social situations that may cause humiliation or embarrassment. While it is one of the common anxiety disorders (Craske et al., 2017), it is a relatively new area of research, and thus, its etiology, effects, and treatment are not clearly understood. Even prevalence rates reported in the literature vary across studies (Antony and Rowa, 2008). For instance, lifetime prevalence estimates for SAD based on large community samples in the United States range from 3 to 13%. In addition, some studies report that SAD has a higher incidence in females than in males (Kessler et al., 2005).

Developmentally, SAD is likely to not only begin in adolescence (mid to late teens) but can also occur earlier in childhood (Somers et al., 2006). A significant number of adults report that they have had problems with social anxiety for their entire lives or as long as they can remember (Brown et al., 2001; Masataka, 2003). A large-scale study of individuals presenting at an anxiety clinic found a mean age of onset of 15.7 years, a number that was younger than the onset of other anxiety disorders (Merikangas et al., 2011).

SAD is best treated with psychotropic medication and cognitive behavioral therapies (CBT), and the most effective treatments are a combination of both (Nordahl et al., 2016). They consist of monoamine oxidase inhibitors, the serotonin reuptake inhibitors, benzodiazepines, and individual cognitive behavioral therapy. CBT typically includes 10–15 weekly sessions and consists of a variety of strategies, such as self-monitoring, psychoeducation, cognitive therapy, exposure-based techniques, and social skills training. While this method has been proven to be effective for SAD if it is executed, it is also true that people with the disorder quite often show unwillingness (Ryan and Warner, 2012) to receive CBT. In fact, a study reported that 92% of individuals with SAD expressed concerns about starting treatment and that is the biggest barrier to treatment that should be overcome (Kessler et al., 2005).

In this regard, preliminary findings reported by a study (Bergamaschi et al., 2011) that investigated the efficacy of CBD with patients with SAD are noteworthy. In that study, 12 patients with SAD were provided with a single dose of CBD (600 mg). When the anxiety induced by simulated public speaking was compared between pretreatment and posttreatment, its level showed a significant decrease after the treatment, whereas no such change was observed in the placebo group of 12 other patients.

The purpose of the current study was to pursue this issue further and to investigate the possible efficacy of CBD as at least an adjunctive option for intervention in people with SAD. While SAD has been classified into several subtypes so far (Antony and Rowa, 2008), here, the author concentrated the research on that with avoidant personality disorder because this subtype is the most commonly diagnosed and is becoming a serious social problem in Japan, where the current study was conducted (Ogino, 2004; Saito, 2007; Teo, 2010). The author attempted to systematically assess the efficacy of CBD in a total of 37 18–19-year-old Japanese with SAD, all of whom had been naive to any form of treatment, by measuring the level of the symptoms of SAD with both the Fear of Negative Evaluation Questionnaire (FNE; Watson and Friend, 1969) and the Liebowitz Social Anxiety Scale (LSAS; Liebowitz, 1987) using an exploratory double-blind parallel-group trial experimental paradigm.

FNE is a 30-item measure of apprehension and anxiety over anticipated social evaluations. This measure uses a true-false scale and is known to show good internal consistency and test-retest reliability (Watson and Friend, 1969). FNE has a range from 0 to 30, with high scores indicating higher levels of social anxiety. LSAS is a short questionnaire to assess the range of social interaction and performance situations feared by a person in order to assist in the diagnosis of SAD (Liebowitz, 1987). It has been commonly used to investigate outcomes in clinical trials and, more recently, to evaluate the effectiveness of psychological treatments (De Gregorio et al., 2019). The scale features 24 items, which are divided into two subscales. Thirteen questions relate to performance, and 11 relate to situations.

The author attempted to assess the efficacy of CBD by comparing the FNE and the LSAS scores measured before the commencement of the 4-week-long intervention (preintervention) and the scores measured after the completion of the intervention (postintervention) in the group of participants who were provided with CBD (the CBD group) and in the group whose participants were provided with placebo (the placebo group). The author hypothesized that CBD would significantly decrease anxiety measured by both of the two scales employed.