The investigation of the psychological impact of using social networks allows the development of strategies to promote mental health. The objective of this study was to evaluate the influence of the sociodemographic variables, optimism, satisfaction with life, affections, and frequency of use of social networking sites (SRS). 257 Brazilians adults participated in this research, 69% of whom were female, with a mean age of 36 years (SD = 15.32). The Positive and Negative Affections Scale (PANAS), the Life Satisfaction Scale (EVS) and the Life Orientation Test (TOV-R) were used. Age was the most significant variable in the participants' results (in the three measures), followed by the time of using social networks (in satisfaction with life and negative affects). Participants who reported using SRS for five hours or more a day, had lower levels of satisfaction with life and higher levels of negative affect. Older people showed higher averages in optimism and satisfaction with life, as well as less negative affect. It was concluded that the frequency of use on social networking sites can negatively influence the subjective well-being of the population, and the increase in age was favorable to the participants' positive mental health.A study of the psychological effects of social networking can be used to develop strategies to promote mental health. In the present study, we evaluated the effects of sociodemographic variables, optimism, life satisfaction, affect, and the frequency of use of social networking websites (SRS). This study involved 257 Brazilian adults, 69 % of whom were females, with a mean age of 36 years (SD = 15.32). Positive and Negative Affects Scale (PANAS), Life Satisfaction Scale (EVS) and Life Orientation Test (TOV-R) were utilized. In the three measures, ages of participants were the most significant factor, followed by their time spent using social media (in terms of satisfaction with life and negative affect). Participants who reported using SRS for five hours or more a day were less satisfied with their lives and suffered from higher levels of negative affect. Elderly people show higher levels of optimism and satisfaction with life, as well as lower levels of negative affect. According to the analysis, using social networking sites frequently can negatively influence the subjective well-being of the population, whereas an increase in age contributed positively to the positive mental health of the participants.L'enquête sur l'impact psychologique de l'utilisation des réseaux sociaux permet le développement de stratégies de promotion de la santé mentale. Le but de cette étude était d'évaluer l'influence des variables sociodémographiques, l'optimisme, la satisfaction à l'égard de la vie, les affections et la fréquence d'utilisation des sites de réseautage social (SRS). 257 Brésiliens ont participé à cette recherche, dont 69% de femmes, avec une moyenne de 36 ans (ET = 15,32). L'échelle d'affections positives et négatives (PANAS), l'échelle de satisfaction de la vie (EVS) et le test d'orientation de la vie (TOV-R) ont été utilisés. L'âge était la variable la plus significative dans les résultats des participants (dans les trois mesures), suivi par le temps d'utilisation des réseaux sociaux (dans la satisfaction de la vie et les affects négatifs). Les participants qui ont déclaré utiliser le SRS pendant cinq heures ou plus par jour avaient des niveaux de satisfaction à l'égard de la vie plus faibles et des niveaux plus élevés d'effets négatifs. Les personnes âgées ont montré des moyennes plus élevées d'optimisme et de satisfaction à l'égard de la vie, ainsi que des effets moins négatifs. Il a été conclu que la fréquence d'utilisation sur les sites de réseautage social peut influencer négativement le bien-être subjectif de la population et l'augmentation de l'âge était favorable à la santé mentale positive des participants.A investigação do impacto psicológico do uso de redes sociais permite o desenvolvimento de estratégias de promoção de saúde mental. O objetivo deste estudo foi avaliar a influência das variáveis sociodemográficas, otimismo, satisfação com a vida, afetos e frequência de uso de sites de redes sociais (SRS). Participaram dessa pesquisa 257 brasileiros, sendo 69% do sexo feminino, com média de 36 anos (DP = 15,32). Foram usadas a Escala de Afetos Positivos e Negativos (PANAS), a Escala de Satisfação com a Vida (EVS) e o Teste de Orientação da Vida (TOV-R). A idade foi a variável de mais significativa nos resultados dos participantes (nas três medidas), seguida pelo tempo de uso das redes sociais (em satisfação com a vida e afetos negativos). Participantes que relataram utilizar SRS por cinco horas ou mais por dia, apresentaram menores níveis de satisfação com a vida e maiores níveis de afetos negativos. Os mais velhos apresentaram maiores médias em otimismo e satisfação com a vida, bem como menos afetos negativos. Concluiu-se que a frequência de uso em sites de redes sociais pode influenciar negativamente o bem-estar subjetivo da população, sendo que o aumento da idade se mostrou favorável à saúde mental positiva dos participantes.