Study timeline according to SPIRIT Statement. BMQ: Beliefs about Medicines Questionnaire; CERQ-27: Cognitive emotion regulation questionnaire-27; COWAT: Verbal Fluency Test; GAD-7: Generalized Anxiety Disorder-7; GSRS: Group Session Rating Scale; IACTA: Inventory of Cognitive Activity in Anxiety Disorders; MCQ-NB: Metacognitions Questionnaire-Negative Beliefs subscale; PHQ-15: Patient Health Questionnaire-15; PHQ-9: Patient Health Questionnaire-9; PHQ-PD: Patient Health Questionnaire-Panic Disorder; PSWQ-A: Penn State Worry Questionnaire-Abbreviated; ROFC: Rey-Osterrieth Complex Figure Test; RRS-B: Ruminative Responses Scale-Brooding subscale; SPWB: Psychological Wellbeing Scale; SDS: Sheehan Disability Scale; TAVEC: Spain-Complutense Verbal Learning Test; TD-CBT: transdiagnostic cognitive-behavioural therapy; TMT: Trail Making Test; WAI-P: Working Alliance Inventory Patient Form; WAIS-IV: Letters and Numbers subtest; WHOQOL-BREF: WHO Quality of Life scale-Brief version.

Study timeline according to SPIRIT Statement. BMQ: Beliefs about Medicines Questionnaire; CERQ-27: Cognitive emotion regulation questionnaire-27; COWAT: Verbal Fluency Test; GAD-7: Generalized Anxiety Disorder-7; GSRS: Group Session Rating Scale; IACTA: Inventory of Cognitive Activity in Anxiety Disorders; MCQ-NB: Metacognitions Questionnaire-Negative Beliefs subscale; PHQ-15: Patient Health Questionnaire-15; PHQ-9: Patient Health Questionnaire-9; PHQ-PD: Patient Health Questionnaire-Panic Disorder; PSWQ-A: Penn State Worry Questionnaire-Abbreviated; ROFC: Rey-Osterrieth Complex Figure Test; RRS-B: Ruminative Responses Scale-Brooding subscale; SPWB: Psychological Wellbeing Scale; SDS: Sheehan Disability Scale; TAVEC: Spain-Complutense Verbal Learning Test; TD-CBT: transdiagnostic cognitive-behavioural therapy; TMT: Trail Making Test; WAI-P: Working Alliance Inventory Patient Form; WAIS-IV: Letters and Numbers subtest; WHOQOL-BREF: WHO Quality of Life scale-Brief version.