Participants will undergo baseline assessment (T0) prior to the intervention, followed by a 4 week Natural Psychotherapy treatment in group setting. The group therapy will be delivered once per week, with each session lasting 2-3 hours. Post-intervention assessment (T1) will be conducted immediately after the completion of the intervention, and a follow-up assessment will be carried out 1 month after treatment termination (T2).

Participants in the control group will receive baseline assessments prior to the waiting period and will continue their treatment-as-usual (TAU) while being placed on a waiting list for 4 weeks. Post-waiting assessment (T1) will be conducted at the end of the waiting period. After T1, the control group patients will receive the same group therapy as the intervention group.

Patients will be divided into 3-4 groups, with each group comprising 8-10 patients, led by one psychotherapist. The intervention will last 4 weeks, with all patients required to participate in weekly face-to-face group sessions, each lasting 2-3 hours. The weekly group sessions are the core of the treatment and consists of two parts: (1) phase-specific psychoeducation on the theoretical principles of Natural Psychotherapy; (2) experiential learning through carefully designed activities to facilitate personal experience and understanding of the theoretical content. Homework is assigned after each group session, such as writing treatment diaries and daily exercise plans. The psychotherapists review patients' treatment diaries daily according to guiding principles and provide feedback, offering key guidance and support. Exercise is emphasized as a core component of active action within the Natural Psychotherapy; participants will develop personalized weekly exercise plans during group ses

The GAD-7 is a brief self-report questionnaire designed to assess the severity of generalized anxiety symptoms (Spitzer et al., 2006). It consists of seven items, with higher scores indicating greater severity of anxiety. Clinical cut-off scores are: 0-4 (minimal/no clinical anxiety), 5-9 (mild), 10-14 (moderate), and ≥ 15 (severe). The Chinese version of the GAD-7 has demonstrated good reliability and validity, with high internal consistency (Cronbach's α = 0.93) and satisfactory test-retest reliability (ICC = 0.71-0.87; Zhang et al., 2021).

The STAI consists of two subscales (Spielberger et al., 1970): the State Anxiety Inventory (S-Anxiety, Items 1-20) and the Trait Anxiety Inventory (T-Anxiety, Items 21-40). The S-Anxiety subscale reflects transient feelings of tension, apprehension and nervousness in response to stressors, while the T-Anxiety subscale assesses relatively stable individual differences in anxiety proneness. Both subscales use a 4-point Likert scale (total scores 20-80), with higher scores indicating higher levels of anxiety; certain items are reverse-scored. The Chinese version shows robust reliability and validity, with high internal consistency (Cronbach's α = 0.91-0.92), strong test-retest reliability (0.76-0.91), and significant correlations with the HAMA (r = 0.69-0.74; Ma et al., 2012).

The IUS is a standard self-report measure for evaluating intolerance of uncertainty (IU). This study uses the 12-item short-form (IUS-12) (Carleton, Sharpe, et al., 2007), which has been validated in Chinese populations (Zhang Y. et al., 2017). Items are rated on a 5-point scale from 0 (not at all characteristic) to 4 (entirely characteristic), with higher total scores indicating higher IU. IUS-12 includes two factors: Prospective IU (Items 1-7) and Inhibitory IU (Items 8-12), though research suggests the total score is a psychometrically sound representation of the construct (Hale et al., 2016; Shihata et al., 2018).