This study evaluated whether cognitive behavioral therapy (CBT), when added to risperidone treatment, improves cognitive function and serum brain-derived neurotrophic factor (BDNF) levels in patients with schizophrenia. Participants were adults with stable-phase schizophrenia who were receiving risperidone therapy. They were assigned to either a control group receiving risperidone alone or an intervention group receiving risperidone plus 10 weekly CBT sessions.

Cognitive function was assessed using the Indonesian version of the Cognitive Assessment Interview (CAI-Ina). Serum BDNF levels were measured from blood samples using an enzyme-linked immunosorbent assay (ELISA). Measurements were performed at baseline and after 10 weeks. The study was conducted at Rumah Sakit Khusus Daerah Dadi, South Sulawesi, Indonesia.

Schizophrenia is a chronic psychiatric disorder associated not only with psychotic symptoms but also with persistent cognitive impairment. Cognitive deficits may affect attention, working memory, verbal memory, processing speed, reasoning, problem solving, and social cognition. These impairments can interfere with daily functioning and long-term recovery. Although risperidone is commonly used as an antipsychotic treatment for schizophrenia, its effect on cognitive function may be limited. Cognitive behavioral therapy (CBT) may provide additional benefit by helping patients identify maladaptive beliefs, develop coping strategies, improve insight, and strengthen adaptive behavior.

This study was designed to evaluate the effect of CBT as an adjunctive therapy to risperidone on cognitive function and serum BDNF levels in patients with schizophrenia. BDNF is a neurotrophic factor involved in neuroplasticity, synaptic function, learning, and memory. Lower BDNF levels have been associated with cognitive impairment in schizophrenia. The study assessed whether adding CBT to risperidone therapy was associated with improvement in cognitive function and changes in serum BDNF levels.

This was an interventional, randomized, single-blind, rater-blind study. Participants were patients with stable-phase schizophrenia treated at Rumah Sakit Khusus Daerah Dadi, South Sulawesi, Indonesia. Eligible participants were adults aged 20 to 50 years with schizophrenia diagnosed according to DSM-5 and PPDGJ-III criteria, illness onset of 5 years or less, stable clinical condition, and ongoing risperidone therapy.

Participants were assigned to two groups. The control group received risperidone therapy. The intervention group received risperidone therapy plus CBT. The CBT intervention consisted of 10 sessions delivered once weekly over 10 weeks, with each session lasting approximately 30 minutes. The CBT sessions included engagement and assessment of target problems, cognitive formulation, exploration of appraisals, evaluation of beliefs, gentle reality testing, development of alternative explanations, behavioral experiments, coping strategy enhancement, insight building, relapse prevention, and future planning.

Cognitive function was measured using the Indonesian version of the Cognitive Assessment Interview (CAI-Ina), an interview-based instrument for assessing cognitive function in patients with schizophrenia. Serum BDNF levels were measured from peripheral blood samples using ELISA. Assessments were performed at baseline and at week 10. The main objective was to compare changes in cognitive function and serum BDNF levels between the risperidone-only group and the risperidone plus CBT group.

Inclusion Criteria:

• Patients diagnosed with schizophrenia according to DSM-5 and PPDGJ-III criteria.
• Illness onset of schizophrenia ≤ 5 years since the first appearance of symptoms.
• Age 20 to 50 years.
• Clinically stable phase, defined as PANSS score 30 to 60.
• Receiving risperidone therapy at a dose of 4 to 6 mg/day.
• Minimum educational level of senior high school.
• Willing to participate in the study and sign informed consent.

Exclusion Criteria:

• Presence of organic comorbid conditions, such as neurological disorders, severe endocrine or metabolic disorders, chronic liver or kidney disease, or systemic infection, that may affect cognitive function or serum BDNF levels.
• History of substance use before hospital admission, except caffeine and nicotine.
• Use of anti-inflammatory drugs, antibiotics, or antioxidant medications.
• Intellectual disability or mental retardation.
• Unwilling to attend cognitive behavioral therapy sessions.

Individual participant data will not be shared because no IPD sharing plan was specified in the approved study protocol, and participant confidentiality will be maintained according to the ethics approval and informed consent procedures.

The outcomes assessor/rater was blinded to participant group allocation. Participants and care providers were not masked because the CBT intervention could not be blinded.