Scientists, however, are still working to understand exactly what happens inside the brain and body when people engage in these practices. People who reported stronger mystical experiences also tended to show greater biological changes. The similarities observed in the meditation study do not mean that meditation and psychedelic drugs produce identical effects. Controlled clinical trials will therefore be necessary before researchers can determine whether the observed biological changes translate into meaningful treatment benefits. Scientists also want to determine how long the biological changes last and whether repeating the interventions can strengthen or maintain them over time.