*2.1. Search Strategy, Study Selection, Inclusion and Exclusion Criteria*

The search for this systematic review with meta-analysis was performed on several electronic databases (PubMed, Web of Science, Scopus and SciELO) during January 2020. These databases were queried using the Boolean operator tools with the following search strategy—((((((depression) OR anxiety) OR post-traumatic stress disorder)) AND ((((((hallucinogens) OR entheogens) OR psychedelics) OR classic hallucinogens) OR serotonergic hallucinogens) OR serotoninergic hallucinogens)) AND (psilocybin) AND ((((((clinical trials) OR human) OR humans) OR man) OR woman) OR patients). The references' lists of the relevant studies were also checked to find further works. Following the PRISMA statement [11], titles and abstracts of the selected articles were initially screened and the full texts of those considered important were subsequently analyzed in detail [12]. The selection process of the studies was performed independently by two authors, with a third being consulted in case of disagreements. The defined inclusion criteria were—studies in humans presenting a true control group; studies in patients with depression and anxiety associated with a life-threatening disease; drug psilocybin; use of Beck Depression Inventory (BDI) to assess depression and/or State-Trait Anxiety Inventory (STAI) to assess anxiety.

BDI was first proposed by Beck et al., 1961 [13] and it is one of the most used scales to assess the severity of depressive symptoms. It is a self-reported questionnaire, consisting on 21 items that measure characteristic attitudes and symptoms of depression. STAI is a self-report questionnaire divided in 2 subscales, called STAI-Trait and STAI-State. STAI allows the detection of the presence and severity of current symptoms of anxiety and a generalized propensity to be anxious. It contains 40 items, 20 of them concerning STAI-State and the remaining 20 concerning STAI-Trait [14].
