This study aims to examine the dual effects of cannabis consumption on both positive and negative symptoms of schizophrenia, across laboratory and real-world contexts. By integrating ecological momentary assessment (EMA) with cognitive tasks such as reality monitoring, the research seeks to clarify how cannabis use influences symptom severity and cognitive functioning in individuals with schizophrenia. Gaining insight into these relationships may contribute to the development of more effective management strategies and ultimately improve outcomes for patients living with schizophrenia.

Schizophrenia is a complex psychiatric disorder that affects approximately 1% of the general population, typically emerging in early adulthood. It is characterized by a wide range of symptoms, including positive symptoms (e.g., hallucinations and delusions), negative symptoms (e.g., apathy and emotional blunting), and cognitive impairments. The disorder contributes substantially to the global burden of disease, ranking among the top 30 causes of disability-adjusted life years.

Cannabis use is common among individuals with schizophrenia, with estimates suggesting that between 16% and 42% of patients have used cannabis at some point in their lives. The relationship between cannabis use and schizophrenia is multifactorial. Cannabis consumption has been associated with an increased risk of psychosis, worsening of positive symptoms, and earlier onset of the disorder. However, some studies indicate that cannabis may also exert beneficial effects on negative symptoms, potentially mediated by compounds other than THC.

Cognitive deficits are a core feature of schizophrenia, particularly impairments in reality monitoring. Reality monitoring refers to the ability to distinguish between internally generated events (intrinsic) and those originating from external sources (extrinsic). In schizophrenia, this capacity is often compromised, leading to misattributions of internal thoughts to external sources, which may contribute to the development of positive symptoms such as hallucinations.

Given the dynamic nature of symptoms and substance use in schizophrenia, traditional clinical models may fail to capture the complexity of these interactions. Ecological Momentary Assessment (EMA) provides a novel approach by leveraging mobile devices to collect real-time data on symptoms, substance use, and cognitive performance in everyday life. EMA has been validated in schizophrenia research, offering high-resolution data that can complement and enhance traditional models.

Inclusion Criteria:

• DSM-5 diagnosis of schizophrenia or schizo-affective disorder with the following clinical features:

  • Clinically stable and in the residual (non-acute) phase of illness,
  • No change in antipsychotic treatment for at least 1 month,
  • Outpatient, ambulatory care,
  • No uncontrolled positive symptoms (assessed using PANSS)

• Patients able to use a mobile phone.

• Capacity and willingness to give informed consent.

• Must be able to read, speak, and understand French

• Patients subscribing to the French national medical insurance.

• Patients under "curatelle" (partial guardianship) are eligible

Exclusion Criteria:

Patient under "tutelle" (full legal guardianship).

• Psychiatric comorbidities: autism, bipolar disorder.
• Current criteria for any other substance use disorder except for nicotine use disorder.
• Any medical condition hindering the study and/or use of the smartphone application.
• Patients with somatic, cognitive or other disorders preventing the use of the device (deafness, impaired vision, illiteracy….).
• Pregnant or breastfeeding woman.
• Patients who are not proficient in French.
• Subject included in clinical and/or therapeutic experimentation in progress.