The goal of the study is to investigate whether adding sulforaphane will benefit the negative symptoms and cognitive function in individuals who have schizophrenia.

This study will compare the sulforaphane with placebo. There is a thirty percent change (less than half) of receiving the placebo. The purpose of including placebo is to judge if the outcome is related to the study medication rather than other reasons.

This study will be carried out in The Third Jiangyin Hospital in China and total of 120 schizophrenia patients with one negative symptom item score of PANSS≥3 will be enrolled into the study. Individuals who participate in the study will be followed for 24 weeks. The changes in clinical symptoms and neurocognitive function will be assessed from baseline (week-0) to week-12, and week-24.

Inclusion Criteria:

1. Meet The Diagnostic and Statistical Manual (DSM-5) diagnostic criteria for schizophrenia;
2. First onset or duration of illness less than 30 years with current symptoms in a stable condition;
3. Male and female aged 18 to 50 years;
4. Total score greater than or equal to 20 on the sum of the seven items constituting the Positive and Negative Syndrome Scale (PANSS) negative symptoms; an item of PANSS negative symptoms >3 scores;
5. Signed the study consent for participation.

Exclusion Criteria:

1. has a history of substance dependence or abuse or whose symptoms are caused by other diagnosable mental disorders;
2. has a history of traumatic brain injury, seizures, or other known neurological diseases of the central nervous system;
3. taking antidepressants, stimulants, mood stabilizers, or received modified electroconvulsive therapy (MECT) or rTMS during the past three months;
4. having current suicidal or homicidal thoughts or any safety concern by research staff that cannot be managed during the trial;
5. taking dementia-related drugs, minocycline, and other drugs that may affect cognitive function;
6. Laboratory tests indicated significant abnormalities in blood routine, liver and kidney function, or other metabolic results;
7. pregnant or lactating women.

Participants and researchers are blind to treatment allocation (double-blind). An independent researcher developed the computer-generated randomization plan.