This cross-sectional observational study investigates structural brain abnormalities in schizophrenia and nicotine use disorder (NUD), with a focus on understanding how these abnormalities correlate with behavioral traits such as decision-making and impulsivity. Schizophrenia is often associated with reduced gray matter (GM) in the prefrontal cortex and anterior cingulate cortex, while nicotine dependence is linked to changes in brain regions involved in reward processing. Nicotine use is particularly prevalent among individuals with schizophrenia, potentially compounding cognitive impairments.

Voxel-Based Morphometry (VBM), an advanced neuroimaging analysis technique, allows for the detection of subtle structural changes in the brain using MRI data. This study aims to utilize VBM to explore GM alterations in three participant groups:

Schizophrenic patients without nicotine dependence

Schizophrenic patients with nicotine dependence

Individuals with nicotine dependence but without schizophrenia

Each group will include 32 participants, making a total sample of 96, calculated using G*Power software assuming a medium effect size, alpha 0.05, and power 0.8. Inclusion criteria include confirmed diagnoses based on DSM-5 and the Fagerström Test for Nicotine Dependence, age 18-60, and MRI compatibility. Exclusion criteria involve other psychiatric or neurological disorders, substance use other than nicotine, and MRI contraindications.

Participants will undergo:

Structural MRI scans

Behavioral assessment using the Barratt Impulsiveness Scale

Clinical interviews using the Structured Clinical Interview for DSM-5

The primary outcome is to identify distinct patterns of GM reduction or alteration across groups, especially in regions involved in decision-making (e.g., prefrontal cortex, anterior cingulate cortex) and reward processing (e.g., ventral striatum). Secondary outcomes include correlating these structural findings with impulsivity and decision-making patterns.

Statistical analysis will be performed using SPSS v26. ANOVA will be used for quantitative comparisons across the three groups, while Chi-square or Fisher's exact tests will compare categorical variables. Pearson's correlation will be used to explore associations between brain changes and behavioral traits. A p-value <0.05 will be considered significant.

Schizophrenia and nicotine use disorder are two conditions linked in part to distinct brain structural abnormalities that can significantly impact cognitive and behavioral functions, particularly in areas like decision-making and impulsivity. Schizophrenia (although it's exact cause is unknown) is often associated with reduced gray matter (GM) in regions such as the prefrontal cortex and anterior cingulate cortex, which are crucial for cognitive control and decision-making processes . Nicotine use disorder, on the other hand, has been linked to structural changes in brain areas involved in reward processing and impulsivity regulation. The overlap of these conditions is notable, as nicotine addiction is highly prevalent among schizophrenic patients, potentially exacerbating cognitive and behavioral dysfunctions .

Voxel-Based Morphometry (VBM) is a widely used neuroimaging technique that enables researchers to detect and quantify brain structural differences, particularly in GM, by analyzing MRI scans. VBM allows for the identification of subtle brain abnormalities that may contribute to the development of schizophrenia and nicotine dependence. These structural changes may provide insight into associated behavioral traits such as impaired decision-making and increased impulsivity, both of which are commonly observed in individuals with either or both conditions

Inclusion Criteria:

• Diagnosed schizophrenia (for groups 1 and 2).
• Nicotine dependence as defined by the Fagerström Test for Nicotine Dependence (for groups 2 and 3).
• Age range: 18-60 years.
• Schizophrenic patients must be stable on medications for at least 2 months.
• Written informed consent (from the patient or his carer).

Exclusion Criteria:

• History of other neurological or other psychiatric disorders (besides schizophrenia or nicotine dependence).
• Current substance use disorders other than nicotine.
• Severe head trauma or other conditions likely to affect brain structure.
• IQ below 70.
• MRI contraindications such as metallic implants (e.g. pace maker), claustrophobia or anxiety disorders severe enough to prevent comfortable MRI scanning will also be exclusion criteria.

The targeted study groups are:

Group 1: Schizophrenic patients without nicotine dependence. Group 2: Schizophrenic patients with nicotine dependence. Group 3: Nicotine use disorder individuals without schizophrenia.

Each group will be matched for age, gender, and educational background to minimize potential confounding variables.