Although decades of research have shown the importance of neurobiological factors in the development of mental health problems in children and adolescents, the translation of this knowledge to use in clinical practice has proven difficult. One of the pitfalls is the false assumption that biological factors are so fundamental that they overrule all other factors and can be used as stand-alone biomarkers or tests for diagnostic purposes and treatment decisions. This assumption is false because all neurodevelopmental disorders result from complex interactions between biology and environment. Therefore, neurobiological assessments should never be used as a shortcut for diagnostic assessments that include the environment, including family, peers, and society at large. Instead, they should be integrated in the diagnostic process. This calls for empirically supported guidance on how to weigh information from neurobiological and psychosocial assessments in the diagnostic and treatment decision process.