Studies show that marijuana is extremely popular among individuals who suffer from psychotic disorders such as schizophrenia. A recent study published in the British Journal of Psychiatry followed 80 marijuana smokers, 42 who had schizophrenia. Over the course of six days, the participants were asked to periodically record their moods. All participants reported feeling generally happier while using marijuana, but the increase was stronger in the group with schizophrenia.
a. Identify the explanatory and response variables.
b. Is this an example of an observational study or an experiment? If observational, is the study retrospective or prospective?