This cross-sectional observational cohort study examined serum α-N-acetylgalactosaminidase levels in methamphetamine use disorder (MUD), methamphetamine-induced psychotic disorder (MP), and healthy control (HC) groups. The study aimed to determine whether decreased α-N-acetylgalactosaminidase levels are associated with psychotic symptoms in methamphetamine users.

Methamphetamine use disorder (MUD) is frequently complicated by the emergence of psychotic symptoms, which may range from transient intoxication-related psychosis to persistent methamphetamine-induced psychotic disorder (MP). Although clinical and biological differences between MUD and MP are increasingly being investigated, the role of α-N-acetylgalactosaminidase, a lysosomal enzyme involved in glycoconjugate metabolism and immune regulation, has not been previously examined in this population.

This cross-sectional observational study aimed to compare serum α-N-acetylgalactosaminidase levels among three groups: patients with methamphetamine use disorder (MUD), patients with methamphetamine-induced psychotic disorder (MP), and healthy control (HC) subjects. A secondary objective was to evaluate associations between α-N-acetylgalactosaminidase levels, psychotic symptom severity, and systemic inflammation, and to assess its potential predictive value for MP diagnosis.

Participants were consecutive inpatients diagnosed with MUD or MP according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR). All patients were admitted to Elazığ Mental Health and Diseases Hospital between May 1, 2025 and August 31, 2025. The healthy control group consisted of individuals without current or past psychiatric disorders or significant medical illnesses. Adult male participants aged 18-65 years were included.

Venous blood samples were collected at hospital admission prior to initiation of treatment. Samples were centrifuged within 30 minutes and serum was stored at -80°C until analysis. Serum α-N-acetylgalactosaminidase levels were measured using a commercially available enzyme-linked immunosorbent assay (ELISA) kit according to the manufacturer's instructions. Routine biochemical analyses and urine toxicology screening were also performed. The Aggregate Index of Systemic Inflammation (AISI) was calculated as (neutrophils × monocytes × platelets) / lymphocytes.

Psychotic symptom severity in the MP group was assessed using the Positive and Negative Syndrome Scale (PANSS). Sociodemographic variables and clinical characteristics, including self-mutilation history, drug use onset age, duration of methamphetamine use, and smoking status, were recorded.

The primary outcome measure was the difference in serum α-N-acetylgalactosaminidase levels among MP, MUD, and healthy control groups. Secondary outcomes included correlations between α-N-acetylgalactosaminidase levels and PANSS scores, associations with systemic inflammation indices (AISI), and evaluation of the predictive performance of α-N-acetylgalactosaminidase (alone and in combination with self-mutilation history) for distinguishing MP from MUD using logistic regression and receiver operating characteristic (ROC) analysis.

The study was conducted in accordance with the Declaration of Helsinki and approved by the relevant institutional ethics committee. All participants provided written informed consent prior to participation.

1. For Methamphetamine Use Disorder (MUD) Group:

   *Inclusion Criteria:

   • Diagnosis of MUD according to DSM-5-TR
   • Medication-free for at least one month prior to admission
   • Age ≥ 18 years and <65 years
   • Provided informed consent

   For Methamphetamine Use Disorder (MUD) Group:

   *Exclusion Criteria:

   • Hypertension

   • Diabetes mellitus
   • Chronic kidney disease
   • Rheumatoid arthritis
   • Systemic lupus erythematosus
   • Cardiac illness
   • Severe neurological disorders
   • Immunological or systemic illness
   • Primary psychiatric disorders other than MUD
   • Alcohol use disorder

2. For Methamphetamine-Induced Psychotic Disorder (MP) Group:

   *Inclusion Criteria:

   • Diagnosis of MP according to DSM-5-TR
   • Medication-free for at least one month prior to admission
   • Age ≥ 18 years and <65 years
   • Provided informed consent

   For Methamphetamine-Induced Psychotic Disorder (MP) Group:

   *Exclusion Criteria:

   • Hypertension
   • Diabetes mellitus
   • Chronic kidney disease
   • Rheumatoid arthritis
   • Systemic lupus erythematosus
   • Cardiac illness
   • Severe neurological disorders
   • Immunological or systemic illness
   • Primary psychiatric disorders other than MP
   • Alcohol use disorder

3. For Healthy Control Group:

   *Inclusion Criteria:

   • No psychiatric diagnosis
   • No systemic or immunological illness
   • Medication-free for at least one month
   • Age ≥ 18 years and < 65 years
   • Provided informed consent

   For Healthy Control Group:

   *Exclusion Criteria:

   • Hypertension

   • Diabetes mellitus
   • Chronic kidney disease
   • Rheumatoid arthritis
   • Systemic lupus erythematosus
   • Cardiac illness
   • Severe neurological disorders
   • Immunological or systemic illness
   • Primary psychiatric disorders other than schizophrenia
   • Alcohol/drug/substance use

The study population consisted of adult male inpatients aged 18-49 years who were admitted to Elazığ Mental Health and Diseases Hospital between May 1, 2025 and August 31, 2025.

The MP group included consecutive inpatients diagnosed with methamphetamine-induced psychotic disorder and the MUD group included consecutive inpatients diagnosed with methamphetamine use disorder according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR).

Both patient groups consisted of active methamphetamine users and were hospitalized for clinical management at the time of assessment. Urine toxicology screening was performed at admission to confirm substance use status.

The Healthy Control (HC) group consisted of adult male individuals without current or past psychiatric disorders and without substance use disorders, matched to patient groups in terms of age and body mass index. HCs had no significant medical illnesses.

Deidentified individual participant data (IPD) underlying the results reported in this study (including demographic variables, serum α-N-acetylgalactosaminidase levels, complete blood count parameters, and Positive and Negative Syndrome Scale (PANSS)) will be made available to qualified researchers upon reasonable request for academic purposes.

Data will be shared after removal of all direct identifiers and in accordance with applicable ethical approvals and data protection regulations. Access to the data will require a methodologically sound research proposal and a data use agreement. Requests should be directed to the corresponding author.

Data will be available beginning 6 months after publication and will remain available for 5 years.

Access will be granted to researchers who provide a methodologically sound proposal. Requests must be approved by the principal investigator and may require a data use agreement in accordance with institutional and ethical regulations.