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General discussion and future perspectives213822q11.2DS would be needed to study the efficacy of treatment interventions for trauma and to identify if and how these interventions need to be adapted to the strengths and weaknesses of individuals with 22q11.2DS. Another example can be found in our study of hearing in chapter 4. About one out of three adults with 22q11.2DS were prescribed hearing aids but reported not to use them.71, 72 Given the high prevalence of hearing loss and the impact it may have on daily life functioning, strategies to increase the use of hearing aids may be examined. Second, longitudinal studies starting in childhood up to late adulthood in individuals with different GNDs are needed to further close the knowledge gap regarding conditions that develop over the life course.46, 62 Since genetic variants associated with GNDs are often identified at an early age, longterm follow up of individuals with these GNDs provides the opportunity to generate knowledge of disease trajectories.73, 74 The need for longitudinal studies starting early in life is further emphasized by the fact that symptoms of late-onset disorders such as motor symptoms of Parkinson’s disease often present after cells, such as dopaminergic neurons, have already died. Ideally, future studies include comprehensive (epi)genetic testing,75detailed phenotyping and assessment of environmental factors (such as diet, physical exercise, stress and trauma)76 in minor to severely affected individuals. In order to obtain adequate sample sizes of individuals with GNDs multi-center and/or consortia studies are required.66 Longitudinal studies are crucial for the identification of early predictors and biomarkers for late-onset disorders, such as proposed in chapter 6, for optimizing screening and monitoring of at-risk groups, and for identifying windows of opportunity for treatment interventions. Qualification of retinovascular and retinoneural parameters as susceptibility biomarkers for psychosis or neurodegenerative disorders in 22q11.2DS depends on whether the change in these parameters explain the change in clinical state (e.g., from normal cognitive functioning to cognitive decline). Therefore, longitudinal studies would be needed to evaluate such parameters as susceptibility biomarkers in 22q11.2DS.Third, cross-GND studies may help to understand differences and overlap between GNDs and identify, potentially shared, underlying mechanisms