The potential effects of substance use on adolescent behavior and brain development are well documented by studies (
1). Adolescence is a vulnerable time for starting a psychiatric disorder such as drug abuse (
2). Drug abuse and depression are the most common disorders that often occur during adolescence (
3).
Craving and negative emotions (such as stress, anxiety, and depression) are the main causes of continued substance consumption and returning to substances after withdrawal (
4). Substance craving is one of the most important diagnostic criteria of substance use disorder (SUD) based on the fifth edition of the diagnostic and statistical manual of mental disorders (DSM-5) (
5). Craving is one of the strongest and most stable causes, among other factors (
6). For people with SUD, craving is the hardest challenge during withdrawal (
7). Adolescents experience significant negative emotions in their lives (
8). Studies show that substance abuse in adolescents is often associated with psychological distress, negative emotions, and psychiatric illnesses (
9). Increasing comorbidity of negative emotions and SUD increases concerns (
10) because depression and anxiety may not only affect the behavior for seeking help and joining the treatment (
11) but also leads to a decrease in the quality of life (
12), increases the risk of relapse (
13), leads to social isolation (
14), and ultimately increases the risk of death (
15). Therefore, modulating drug craving and negative emotions (anxiety, stress, and depression) is seemed to prevent substance use in adolescents. The self-medication hypothesis introduced by Khantzian suggests that people use drugs and alcohol to regulate their emotions, such as anxiety, depression, stress, pain, loneliness, and so on (
16).
Transcranial direct current stimulation (tDCS) is one of the main techniques for modulating brain activity and cortical excitability, which involves the use of a low-intensity electrical current over the scalp (
17). Recently, some research has studied the implementation of tDCS for children and adolescents with various neuropsychiatric disorders. This new relevant literature addresses both safety and potential therapeutic efficiency in children and adolescents (
18). Also, the interest has increased in non-invasive methods for stimulating brain activity in the treatment of addiction (
19). Thus, tDCS has been used in numerous studies for improving negative emotions such as depression (
20).
Today, mindfulness training is considered a promising treatment for various substance abuse disorders (
21). Previous studies suggest that mindfulness-based interventions (MBIs) improve substance use disorders by increasing the cognitive regulation of several activity processes, including making clear cognitive appraisals and moderating negative emotions to decrease permanent cognition and emotional arousal, increasing cognitive to reduce drug-related attentional bias, reducing cue reactivity, and increasing cognitive control over craving (
22).
Although tDCS can be effectively used as an alternative therapy, new studies have suggested it as a “strengthening therapy” to promote the effectiveness of other psychotherapy treatments (
23). To investigate the efficacy of tDCS in combination with psychotherapy for the treatment of MD, Nejati et al. (
24) proposed a new therapeutic approach called Psychological Intervention Combined with direct current electrical stimulation (PIN-CODES).
The review of the related studies shows that both mindfulness and tDCS are independently effective in treating addiction. Studies have also shown that the stimulation of the frontal area of the brain can enhance the effects of mindfulness by improving working memory (
25). One hypothesis is that combining mindfulness therapy with electrical stimulation can have synergistic effects (
26), but it has not yet been studied.
In the present study, we evaluated the effects of mindfulness (as a psychological intervention), tDCS, and the combination of tDCS and MBSAT (PIN-CODES) on negative emotions and reducing craving in adolescents with methamphetamine use disorders. Also, we expect tDCS + MBSAT to have longer-term effects compared to other treatments, especially tDCS (
22-
26).