Levels of cannabis use are high during adolescence, but the proportion of cannabis users among adults is also progressing, often for medical reasons. This study describes the reasons and motivations for using medical cannabis among adults over 30 years old in France. This qualitative study was performed using an interpretative phenomenological analysis. People with a history of cannabis use or current cannabis users were recruited from the TEMPO cohort. Homogeneous purposive sampling was applied among those using medical cannabis. Twelve participants, among thirty-six who reported using cannabis for medical reasons, were selected and interviewed. Five superordinate themes were identified in the analysis: 1—soothing a traumatic experience through cannabis use; 2—an ambivalent relationship with the user and cannabis and with the user and close relatives; 3—cannabis, a known soft drug comparable to alcohol or tobacco, leading to an illogical demonization; 4—recreational use in the context of experimentation; and 5—a paradoxical desire for exemplary parenting. In this first recent study to describe the reasons and views adults have in order to continue using cannabis after 30 years of age, we identified ways to explain this consumption. The internal appeasement provoked by cannabis stems from a struggle to appease a violent external situation.