2.1 Clinical data
We retrospectively analyzed the clinical characteristics of 61 subjects with methylphenidate use disorder (aged 16–27 years, according to the criteria of stimulant use disorder of DSM-5 diagnosis) who were admitted to the Beijing Gaoxin Hospital drug rehabilitation program from Jan 2017 to Mar 2019. The drugs that patients administrated was “NOVARTIS” Ritalin. Patients medication history were obtained through self-report or from their parents. There was no concurrent use of other medications. All the participants were screened for Magnetic resonance imaging (MRI) and a range of psychiatric symptoms on admission, such as Brief Psychiatric Rating Scale (BPRS), Scale for Assessment of Positive Symptoms (SAPS), Scale for Assessment of Negative Symptoms (SANS), Bech-Rafaelsen Mania Rating Scale (BRMS), and DSM-5 diagnostic criteria for Attention-Deficit/Hyperactivity Disorder (ADHD), to rule out other psychiatric disorders. No subject had attention-deficit/hyperactivity disorder (ADHD) or any other major psychiatric disease. All subjects reported a long history of methylphenidate oral administration at high doses and exhibited withdrawal symptoms after cessation. All patients continuously took methylphenidate before or on the day of admission, according to the self-report and parents report. The patients were hospitalized with psychotherapy and medication. In the medication treatment, patients with sleep disorders were prescribed benzodiazepines (estazolam; Apazolam; chloritazepam), Imidazole pyridine (Zonpyrenite) and The third generation of the hypnotic drug of the cyclopyrrosterone. Patients with anxiety symptoms took benzodiazepines (Laura zipani) and non-benzodiazepines antianxiety drug (buspirone). Patients with depression symptoms were prescribed Serotonin reuptake inhibitors, Citalopram, paroxetine and Atypical antidepressants, such as trazodone. The medication was given according to patients individualized conditions. In the psychotherapy, mindfulness therapy and cognitive behaviour therapy were applied. Four participants were discharged after two weeks of treatment, 11 were discharged after three weeks of treatment, and the remaining 46 participants were discharged after four weeks of treatment. The study was approved by the Ethics Committee for Medical Research of Beijing Gaoxin Hospital.
2.2 Neuropsychological evaluations
Upon admission to the hospital, information about drug use was collected, and the Social Support Self-Rating Scale (SSRS)(13), General Self-Efficacy scale (GSE)(14), and drug use motivation scale(15) were administered. The Hamilton Depression Rating Scale, Hamilton Anxiety Rating Scale and the DSM-5 measure were administered by one specialized psychiatrist each week during the 4-week rehabilitation program.
The Social Support Self-Rating Scale (SSRS) is one of the most commonly used instruments for measuring social support in China. The scale has three dimensions: subjective support, objective support and support-seeking behavior. The total SSRS score ranged from 12 to 66. A higher score indicates a higher level of perceived social support.
The drug use motivation scale has six dimensions: social pressure, values to drug use, environmental factors, physical symptoms, negative emotion and high sensation-seeking. The total score ranged from 32 to 224. A higher score indicates a higher level of drug use motivation.
For the Hamilton Depression Rating Scale (HAMD-17), a total score ranging from 0–7 was considered normal, scores ranging from 8–16 indicate mild depression, scores ranging from 17–23 indicate moderate depression, and scores greater than 23 indicate severe depression. The HAMD-17 contains five factors: (1) anxiety/somatic, (2) weight, (3) cognitive dysfunction, (4) stuck, and (5) sleep difficulty.
For the Hamilton Anxiety Rating Scales (HARS), a total score ranging from 0–6 indicates a normal condition, scores ranging from 7–13 indicate mild anxiety, scores ranging from 14–20 indicate moderate anxiety, and scores above 20 indicate severe anxiety.
2.3. Statistical analysis
All data analysis was performed with R Studio 126.96.36.199 (RStudio, Inc) and SPSS v. 21 (IBM Corp., NY, USA). Pearson’s and Spearman’s correlation analyses were used to analyze the relationship between demographic information and clinical outcomes of participants. Kernel density curve estimation was used to explore the distribution of participants' demographic data, such as age, Body Mass Index (BMI), and age at first drug use. Pearson’s correlation analysis was used to examine the correlation between baseline levels and posttreatment levels of anxiety and depression, as well as BMI and daily dosage (gram). Three linear regression models were employed to investigate the potential predictors for daily dosage, depression and anxiety. In model 1, the dependent variable was the daily dosage, and the independent variables were addiction year and total score of drug use motivation, social support self-rating scale and self-efficacy scale. In model 2 and 3, the dependent variables were depression and anxiety score separately. The independent variables were daily dosage, the total score of drug use motivation, social support and self-efficacy. The overall statistical significance threshold was set as two-tailed, p < 0.05.