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L-Theanine adjunct to risperidone in the treatment of chronic schizophrenia inpatients: a randomized, double-blind, placebo-controlled clinical trial.

  • 2023-09-12
  • Psychopharmacology 240(12)
    • Ahmad Shamabadi
    • Setareh Fattollahzadeh-Noor
    • Bita Fallahpour
    • Fatemeh A Basti
    • Mohammad-Reza Khodaei Ardakani
    • Shahin Akhondzadeh

Study Design

Type
Randomized Controlled Trial (RCT)
Population
80 chronic schizophrenia inpatients
Methods
randomized, parallel-group, double-blind, placebo-controlled trial; 8 weeks of risperidone (6 mg/day) plus either L-theanine (400 mg/day) or matched placebo
Blinding
Double-blind
Duration
8 weeks

Rationale

Inadequate responses to current schizophrenia treatments have accelerated research into novel therapeutic approaches.

Objectives

This study investigated the efficacy and tolerability of adjunctive L-theanine, an ingredient with neuroimmunomodulatory and neuroprotective properties, for chronic schizophrenia.

Methods

Eighty chronic schizophrenia inpatients were equally assigned to receive risperidone (6 mg/day) plus either L-theanine (400 mg/day) or matched placebo in this 8-week, randomized, parallel-group, double-blind, placebo-controlled trial. The participants were assessed using the Positive and Negative Syndrome Scale (PANSS) by recording the results of subscales at baseline and weeks 4 and 8 to measure treatment efficacy. Additionally, the participants were assessed for the Hamilton Depression Rating Scale (HDRS) and adverse events, including the Extrapyramidal Symptom Rating Scale (ESRS).

Results

Sixty patients, 30 in each group, were included in the analyses. All baseline demographic and clinical characteristics were comparable between the groups (p-values > 0.05). The reduction rates from baseline to endpoint in negative, general psychopathology, and total scores of PANSS were greater in the L-theanine group (p-values = 0.03, 0.01, and 0.04, respectively). Regarding general psychopathology scores, the reduction in the L-theanine group was also greater until week 4 (p-value < 0.01). The time × treatment interaction effect was significant on negative (p-value = 0.03), general psychopathology (p-value < 0.01), and total (p-value = 0.04) scores of PANSS, indicating additional improvements in the L-theanine group. The HDRS and side effects were comparable between the groups (p-values > 0.05).

Conclusions

L-Theanine adjunct to risperidone safely and tolerably outperformed adjunctive placebo for schizophrenia, and promising evidence indicated its effects on primary negative symptoms, which need to be scrutinized in further studies.

Trial registration

The study protocol was registered and published prospectively in the Iranian Registry of Clinical Trials ( http://www.irct.ir ; registration number: IRCT20090117001556N133) on 2020-12-12.

Research Insights

  • L-Theanine→Reduced General Psychopathology Score

    The reduction rates from baseline to endpoint in... general psychopathology... scores of PANSS were greater in the L-theanine group (p-values = 0.01...). The time × treatment interaction effect was significant on... general psychopathology... scores of PANSS (p-value < 0.01)

    Effect
    Beneficial
    Effect size
    Small
    Dose
    400 mg/day
  • L-Theanine→Reduced Hamilton Depression Rating Scale Score

    The HDRS... were comparable between the groups (p-values > 0.05).

    Effect
    Neutral
    Effect size
    Small
    Dose
    400 mg/day
  • L-Theanine→Reduced Negative Symptom Score

    The reduction rates from baseline to endpoint in negative... scores of PANSS were greater in the L-theanine group (p-values = 0.03...). The time × treatment interaction effect was significant on negative... scores of PANSS (p-value = 0.03)

    Effect
    Beneficial
    Effect size
    Small
    Dose
    400 mg/day
  • L-Theanine→Reduced Total PANSS Score

    The reduction rates from baseline to endpoint in... total scores of PANSS were greater in the L-theanine group (p-values = 0.04...). The time × treatment interaction effect was significant on... total... scores of PANSS (p-value = 0.04)

    Effect
    Beneficial
    Effect size
    Small
    Dose
    400 mg/day

Adverse Events Reported

  • L-Theanine→Overall tolerability

    The HDRS and side effects were comparable between the groups (p-values > 0.05).

    Finding
    No significant difference
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