N-acetylcysteine (NAC) for Improving Cognitive Dysfunction in Schizophrenia

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

COMPLETED

Clinical Phase

PHASE1

Total Enrollment

26 participants

Study Classification

INTERVENTIONAL

Study Start Date

2013-06-30

Study Completion Date

2014-05-31

Brief Summary

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This study will evaluate the effect of the dietary supplement N-acetylcysteine (NAC) on electrophysiologic (EEG) markers related to cognition, as well as performance on psychological tests measuring cognition. The primary hypothesis is that participants treated with NAC will show improvements in cognitive function, as measured by EEG and performance-based tests.

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Detailed Description

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Schizophrenia is a serious mental illness associated with substantial social and occupational dysfunction. While positive psychotic symptoms of schizophrenia often respond to antipsychotic medications, negative symptoms and cognitive impairment are difficult to treat, necessitating novel interventions. Cognitive deficits are an important treatment target because the degree of cognitive impairment is a critical predictor of work, education, and social functioning.

Glutamatergic receptors are among the most promising biological targets for cognitive-enhancing drugs in schizophrenia. Abnormal glutamatergic signaling has long been thought to be important in the pathophysiology of schizophrenia; specifically, reduced NMDA glutamatergic receptor activity on thalamic inhibitory neurons disinhibits glutamatergic neurons projecting to the cortex, which can cause secondary dopaminergic abnormalities and lead to characteristic symptoms, including cognitive deficits. Many electrophysiological (EEG) biomarkers related to cognitive dysfunction in schizophrenia are thought to be linked to deficient NMDA glutamatergic neurotransmission. Additionally, neuroplasticity is thought to involve glutamatergic signaling. This pattern of linkages suggests that correcting impaired NMDA glutamatergic transmission in schizophrenia could lead to enhanced cognitive function and learning.

In this pilot study, we will focus on a promising dietary supplement approach to address glutamatergic deficits, evaluating its effects by EEG biomarkers and performance-based neurocognitive assessments. N-acetylcysteine (NAC) is a modified amino acid that is commonly used as a dietary supplement because of its antioxidant properties. NAC modulates glutamatergic signaling as follows: In the CNS, glial cells take up NAC via cystine-glutamate antiporters, which in turn leads to increased glutamate efflux into the extracellular space. Extracellular glutamate binds to non-synaptic glutamate receptors such as the metabotropic glutamate receptors (mGluR) type 2/3 and type 5. The net result of these events is a normalization of pathologically elevated cortical glutamate levels.

We will assess EEG biomarkers associated with cognitive deficits in schizophrenia, including a recently-described biomarker for visual cortical plasticity. We will also perform a comprehensive assessment of neurocognition with the MATRICS battery, which could suggest whether certain cognitive domains are sensitive to improvement with NAC therapy.

Our primary aim is to determine whether NAC administration will improve NMDA-dependent EEG abnormalities in schizophrenia. We have 3 hypotheses: (1) NAC administration will increase mismatch negativity amplitude as compared to placebo; (2) NAC administration will increase P300 amplitude as compared to placebo; and (3) NAC administration will increase gamma oscillation power and phase synchronization as compared to placebo. We also will examine whether NAC will improve measures of visual neuroplasticity, performance-based measures of neurocognition, and clinical symptoms of schizophrenia.

Conditions

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Schizophrenia

Study Design

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Allocation Method

RANDOMIZED

Intervention Model

PARALLEL

Primary Study Purpose

TREATMENT

Blinding Strategy

QUADRUPLE

Participants Caregivers Investigators Outcome Assessors

Study Groups

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N-acetylcysteine (NAC)

Capsules containing N-acetylcysteine 600mg, with inactive ingredients of cellulose, L-leucine, and silica used as filler. Dosage is 2 capsules by mouth twice daily for 8 weeks.

Group Type EXPERIMENTAL

N-acetylcysteine (NAC)

Intervention Type DRUG

Inactive placebo capsule

A placebo capsule is used that is identical to the active treatment but lacks NAC. The inactive ingredients in the placebo capsule are cellulose, L-leucine, and silica. Dose is 2 capsules by mouth twice daily for 8 weeks.

Group Type PLACEBO_COMPARATOR

Inactive placebo capsule

Intervention Type DRUG

Interventions

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N-acetylcysteine (NAC)

Intervention Type DRUG

Inactive placebo capsule

Intervention Type DRUG

Other Intervention Names

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N-acetyl-L-cysteine NAC Placebo capsule Sugar pill

Eligibility Criteria

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Inclusion Criteria

1. Meets DSM-IV-TR criteria for schizophrenia.
2. At least 3 months since any psychiatric hospitalization
3. At least 1 month since meeting criteria for having a major depressive episode
4. At least 6 months since any behaviors suggesting any potential danger to self or others
5. Currently prescribed an antipsychotic medication, with dose not varying \>50% over 3 months prior to study participation
6. No acute medical problems that could interfere with study participation
7. Chronic medical problems consistently treated and stable for at least 3 months prior to participation
8. Ability to provide informed consent and cooperate with study procedures

Exclusion Criteria

1. Documented history of IQ less than 70 or severe learning disability
2. History of treatment with electroconvulsive therapy within 6 months prior to study participation
3. History of neurological or neuropsychiatric condition (e.g., stroke, severe traumatic brain injury, epilepsy, etc.) that could confound assessments
4. Documented history of persistent substance abuse or dependence within 3 months prior to study participation

Minimum Eligible Age

18 Years

Maximum Eligible Age

65 Years

Eligible Sex

ALL

Accepts Healthy Volunteers

No