This study analysed the 48-week follow-up data from a published randomised controlled trial (RCT) protocol[33] that compared the effectiveness of CBT between CBT combined with medication (CBT+M) group and medication (M)-only group. The protocol of the original study was registered at ***, and the registration identification number is ***. This study received ethics approval from the ethics committee of ***, and all participants signed informed consent forms.
Participants
Participants were outpatients of *** and individuals recruited from the Internet from March 2019 to November 2019. All participants received a diagnostic interview by psychiatric physicians via Conners’ Adult ADHD Diagnostic Interview for DSM-IV (CAADID) [34]. The symptoms during childhood were confirmed based on the recall of the participants as well as the reports of parents or other major caregivers. The key inclusion criteria were as follows:
1) Aged 18-45 years old with a diagnosis of adult ADHD through Conners’ Adult ADHD Diagnostic Interview[34].
2) Stable use of medication (drug fluctuations < 10% for at least 1 month)[35], either methylphenidate hydrochloride controlled-release tablets (Concerta®) or atomoxetine hydrochloride (Strattera®).
3) With residual symptoms since they were scaled with Clinical Global Impression Scale (CGI-S) ≥ 3.
The key exclusion criteria were as follows:
1) Patients with current severe mental disorders, including psychotic disorders, current mania episodes of bipolar disorder, severe depressive episodes with psychotic symptoms or high risk of suicide/self-injury, severe panic disorder, substance abuse, and antisocial personality disorder.
2) Those with a full-scale intelligence quotient (IQ) < 80.
3) Those with suicide risk.
4) Those with unstable physical conditions (such as diabetes, angina pectoris, hypertension, or active hepatitis).
5) Prior or present participation in other psychological therapies.
Patients who attended < 7 times or those who switched to other treatments were considered withdrawn from the study.
The flowchart of participants from baseline to 48-week follow-up is presented in Figure 1. A total of 372 subjects interested in the study were contacted, of whom 193 (51.88%) underwent the baseline assessment, and the remaining 98 participants who met the inclusion criteria were randomized to either the CBT+M group (n = 49) or the M-only group (n = 49). The CBT+M group engaged in 12 weeks of group CBT, and the M-only group waited and received basic clinical management. Forty-eight-week follow-up data were obtained from 87.76% (43/49) of the CBT+M group and 89.80% (44/49) of the participants in the M-only group.
All participants recruited were under assessment by psychiatrists blinded to treatment assignment, and an independent statistician conducted the randomization. The assessors were postgraduate students of psychiatry who had received unified training to use all the measurement tools, and the consistency was rated.
Measures
Diagnostic interview and intelligence quotient (IQ) evaluations
Conners’ Adult ADHD Diagnostic Interview for DSM-IV (CAADID) [34] and structured clinical interviews for DSM-IV Axis-I and Axis-II [36] were used to assess ADHD diagnosis and the comorbid disorders at the baseline assessment. The Wechsler Adult Intelligence Scale-Revised in China (WAIS-RC) [37] was used to estimate the full-scale IQ (FIQ).
ADHD core symptoms
The self-reported ADHD Rating Scale (ADHD-RS) [38] was used to evaluate the ADHD core symptoms. The higher the total score, the more severe the core-symptom impairment.
Depressive symptoms
The Self-rating Depression Scale (SDS) [39] was used to assess depressive severity. A higher score indicates more severe depressive symptoms.
Maladaptive cognitions
The Automatic Thoughts Questionnaire (ATQ)[40] was used to evaluate the frequency of spontaneous negative thoughts, and the Dysfunctional Attitude Scale (DAS)[41] was used to measure individuals' depressogenic assumptions or beliefs. A higher score indicates more maladaptive cognitions related to depressive symptoms.
Quality of life
The World Health Organization Quality of Life-Brief Version (WHOQOL-BREF) [42, 43] was used to evaluate the degree of life satisfaction in four dimensions. We used the psychological domain score to estimate the psychological quality of life (QoL-psychological domain). Higher scores indicate higher levels of QoL.
Interventions
The 12-week group CBT program had a detailed introduction in the protocol[33]. The modules on organization and planning, coping with distractibility, restructuring maladaptive cognitions, and dealing with procrastination were mainly discussed. All participants attended CBT organized by the same psychotherapy team who had received systematic training and regular supervision to deliver the program. Each CBT group consisted of 7 to 12 patients, a leader, and a co-leader who cooperated together. The weekly CBT continued for 12 weeks and involved one 120-minute session each week. Each treatment session started with a review of homework and group-based reflection on ADHD and related symptoms, and then new skills learning and discussion were performed, and homework was arranged.
The M-only group received basic clinical management based on their own needs in the outpatient clinic, including medical consultation and nonpharmacological consultation not related to CBT treatment.
Due to the study design, the participants were asked to maintain stable use of medication during follow-up, but best clinical practices were followed, which resulted in some changes. Thus patients were asked to report their use of medication at each time estimation.
Statistical analyses
First, independent two-sample t-tests for continuous data and χ2 tests for categorical data were performed to compare the baseline variables. Then, mixed linear models (MLMs) were conducted to analyse the effects between the two groups at the 48-week follow-up including dimensions of ADHD core symptoms (ADHD-RS total score), depressive symptoms (SDS score), maladaptive cognitions (ATQ and DAS total scores), and psychological QoL (QoL - psychological domain score). The baseline characteristics were used as covariates if differences were found between groups. The statistics were based on an intent-to-treat (ITT) analysis, and multiple imputations (data were imputed 5 times) were conducted in the original dataset to address the missing data [44].
The change of ADHD core symptoms, depressive symptoms, maladaptive cognitions, and QoL at 48-week follow-up from baseline were then collected. To explore the mechanism of CBT, Pearson’s correlation was used to assess the correlation among score changes of the above dimensions both in the CBT+M and M-only groups. Irrelevant, weak, moderate, and strong correlations (r) were defined as r values of 0-0.09, 0.10-0.30, 0.30-0.50, and 0.50-1.00, respectively. Structural equation mediation model analyses (SEM) were then performed using the R package lavaan[45] with the R software (Version 4.2.2) to test the influence of CBT on changes in psychological QoL via ADHD core symptoms, depressive symptoms, and maladaptive cognitions. The mediation analysis was controlled for baseline dimension indicators (such as age, gender, years of education, FIQ, etc.) if differences between groups were found. Model fit was assessed using the confirmatory fit index (CFI) [46], root mean square error of approximation (RMSEA), and standardized root mean square residual (SRMR)[47]. CFI > 0.95 and RMSEA < 0.06 are viewed as supporting good model fit.