A systematic search was conducted involving all pairwise combinations of Acne vulgaris and these items: ‘‘quality of life’’, ‘‘brain-derived neurotrophic factor’’, ‘‘BDNF’’, ‘‘depress*’’, ‘‘anx*’’, ‘‘psychiat*’’, ‘‘psycho*’’, ‘‘phobia’’, ‘‘stress’’, ‘‘suicide’’, ‘‘loneliness’’, ‘‘self-esteem”. The gene discussed is BDNF; the disease is phobic disorder.