What type of variability is this referring to? Is it only a moderator variable? "The researchers investigated several adverse outcomes related to mental health following wildfires, including "anxiety, depression, insomnia, sleep quality, nightmares, and post-traumatic stress disorder (PTSD) symptoms" (Isaac et al., 2024). These outcomes were measured using established assessment tools: the Disturbing Dream and Nightmare Severity Index (DDNSI), Generalized Anxiety Disorder Questionnaire (GAD-7), Insomnia Severity Index (ISI), Patient Health Questionnaire (PHQ-9), Pittsburgh Sleep Quality Index (PSQI), and PTSD Checklist (PCL-5). These tools provided a comprehensive evaluation of the psychological and sleep disturbances experienced by the participants.

The study methodology involved comparing wildfire survivors from the USA, Australia, and Canada to identify differences in mental health outcomes. Results indicated that participants from the USA scored higher on measures of anxiety (GAD-7), insomnia (ISI), and PTSD symptoms (PCL-5) compared to those from Australia and Canada. This finding underscores the variability in mental health impacts among wildfire survivors across different countries."