In the present study, we used a machine-learning approach to establish prediction models and analyzed the related influencing factors of clients’ side effects perceived by therapists based on a primary online survey in China. The results demonstrated that 59.6% of the therapists reported some side effects in the psychotherapy that they were carrying out, and the most common side effect perceived by the therapists was “made the clients or patients feel bad” (49.8%). The random forest–based classifier provided the best predictive performance in distinguishing between the therapists with and without perceptions of clients’ side effects, with an F1 score of 0.722 and an AUC value of 0.717. The SHAP analysis further showed that “therapists’ psychological activity” was the most relevant feature distinguishing the two categories of therapists.
The identification and management of side effects by therapists is the key to performing professional psychotherapy. A limited sample study (n = 73) showed that, although 94.5% of clinicians agreed that negative effects of psychological treatments exist and 75% of clinicians described that they had clinical experience with negative effects, only 8 (11%) of clinicians had received information about negative effects during their basic clinical training . In our study, the accuracy of identifying side effects by therapists was significantly higher than that of previous studies [9–11], which indicates that the sensitivity of therapists to side effects is increasing. In China, the National Health Commission promulgated the Code of Psychotherapy in 2013, and the Chinese Psychological Society formulated the Code of Ethics for Clinical and Counseling Psychology (2nd Edition) in 2019. The professional training of psychotherapists is increasingly becoming systematic and standardized, but there is no information about the side effects of psychotherapy in the process of training therapists in China  or even worldwide . Licensed therapists may be able to identify and manage side effects in psychotherapy to ensure the professionalism and standardization of the psychotherapy industry. This is also the primary purpose of this study, but much work remains to be done.
In our investigation, “made the clients or patients feel bad” (49.8%) was the most common perception of the side effects reported by the therapists, which is consistent with previous studies [6, 41–43]. Qualitative research focusing on the therapists’ perspectives on the negative effects of psychological treatments demonstrated that the characteristics of the negative effects included “short-term negative effects”, “no treatment effect”, “deterioration”, “dependency” and “impact on other life domains” . The negative effect “deterioration” was a common side effect of psychological treatments. Among the few quantitative studies on therapists' experiences, 100 cognitive behavior therapists were interviewed for side effects in their current outpatients . These therapists reported that the most frequent side effects were "negative wellbeing/distress" (27%), "worsening of symptoms" (9%) and "strains in family relations" (6%). Similar outcomes of psychotherapy have been found in other studies based on clients’ experiences. A survey conducted by our team at nearly the same time as this study revealed that the most common side effect experienced by the clients was “feel bad in psychotherapy” (24.6%) . These negative emotions caused by psychotherapy might last for a long time. After an average of 3.76 years (outpatients) and 9 months (inpatients) of psychotherapy, the negative emotions elicited by the question “I was hurt by what the therapist said to me” were still the most frequently recognized side effects in outpatients (3.6%) and inpatients (20.3%) . In the PSEQ-T, “feel bad” referred to a negative emotion experienced by participants in psychotherapy, such as anxiety, tension, sadness, and anger. With the emergence of new symptoms in the process of psychotherapy, these negative feelings may be related to therapists, patients and the therapeutic alliance . If these side effects are not identified and managed well by therapists, psychotherapy may induce harm.
The side effects of psychotherapy have adverse effects on patients, and their occurrence should be minimized during psychotherapy. The question is how to identify patients with potential side effects by psychotherapy and therapists who can perceive the side effects of psychotherapy. In our previous work, we used ML to identify clients who may have side effects from psychotherapy. The F1 value of the model was 0.797, and the AUC was 0.804, indicating that the model had a good predictive effect . Therapists can use this information to provide more suitable psychotherapy for specific patients, thereby improving the outcomes of psychotherapy. Similarly meaningful would be if we could use ML to distinguish between therapists who can and cannot perceive the side effects of psychotherapy. In this study, we used a self-compiled questionnaire to extract features from three dimensions (symptoms, relationships, and social functions). A random-forest algorithm-based model achieved an F1 score of 0.722 and an AUC value of 0.717, which demonstrated that the model can be used to distinguish among therapists with different perceptive abilities. With the information the model provides, on the one hand, our results can screen therapists and find those with better awareness of the side effects of patient psychotherapy; on the other hand, therapists with relatively poor perception can be provided the relevant training to improve the professionalism of psychotherapy.
Furthermore, we calculated the |SHAP value| of each feature in the random forest–based model. In this model, the therapists believed that their “psychological activity may be the cause of the side effects in psychotherapy”, and these therapists were the most sensitive to the side effects. Some studies based on clients’ experiences also found that the characteristics of therapists can predict the side effects in psychotherapy [6, 16, 17]. Therapist factors mediate the outcomes of psychotherapy mainly through therapeutic alliances. On average, therapists who developed stronger alliances with their patients achieved better therapeutic results . According to Jennifer, Jonas and Sylke , the destructive therapeutic alliance was particularly evident in the therapists’ mental state performance, such as controlling and challenging statements. A good therapeutic alliance values a supportive and reinforcing context, as in a context in which fewer stressful interventions occur and the therapeutic relationship is comfortable. The therapist's mental activity had an effect on the clients through the therapeutic relationship, which was the most critical factor related to psychotherapeutic side effects . Combined with previous research results, the present study suggested that the therapist's introspection and management of their own psychological activity will help the therapist to identify and monitor the side effects in psychotherapy, which could significantly reduce the deterioration effect  and improve the effect of psychotherapy .
In this study, two other important predictors were the therapist's perception of the factors “characteristics of psychotherapy techniques were a possible cause of the side effects in psychotherapy” and “improper use of psychotherapy techniques was a possible cause of the side effects in psychotherapy”. The essence of psychotherapy is to help people learn who they are, access their emotional basics, hold their feelings intact and be able to think even under the heaviest interpersonal pressure, which is the first and main therapeutic goal . In addition to the factors of therapists and clients, the theory and technology of psychotherapy are key to the effect of treatment. Parry and her colleagues  believe that “using an inappropriate therapeutic method or errors in delivering a recommended therapy” might be risk factors for negative outcomes and possible mechanisms for harmful psychological therapies. Some studies have shown that the theoretical orientation of psychotherapy significantly affects the occurrence of side effects [4, 6]. For example, patients who experienced a poor therapeutic relationship, a high degree of dependency or isolation and a high burden through psychotherapy were more frequently treated in psychodynamic therapies . Although such a therapeutic process is effective, it places great pressure on patients. Furthermore, an inappropriate use of psychotherapy techniques may lead to malpractice and unethical behavior in psychotherapy. At least one case of malpractice and unethical behavior was reported by 28.8% of inpatients and 7.1% of outpatients in psychotherapy . Therefore, this study indicates that understanding the limitations of psychotherapy theory and technology will help therapists identify the side effects of psychotherapy.
To the best of our knowledge, this was the first study to predict the potential side effects perceived by therapists in psychotherapy using ML. The machine-learning approaches described in this study are sufficiently accurate and meaningful to be integrated into clinical psychiatry. Our research provides new methods that can be used to distinguish among therapists with different perceptions of clients’ side effects and suggests important predictive factors that affect the therapist's perception. The results of this study demonstrate verify a possible technical path that can enhance the sensitivity and recognition of therapists to the side effects in psychotherapy. In this path, the stability and health of the therapist's psychological state and professional mastery, especially the mastery of the limitations of treatment theory and technology, may help to increase the recognition and management of side effects.