The HELIUS study is conducted by the Academic Medical Center (AMC) in close collaboration with the Public Health Service of Amsterdam (GGD Amsterdam). Researchers from various departments of the AMC, the GGD Amsterdam and several other institutions and universities are participating in the study. The HELIUS study is open to proposals of collaboration with external research groups. Requests for collaboration The study has an open policy in regard to collaboration with other research groups. Before access to data is provided, all researchers should carefully read and must adhere to the HELIUS Collaboration Policy. In brief, a research proposal or publication proposal must be developed following the proposal formats. All proposals should then be submitted to the HELIUS Scientific Coordinator (Dr.ir. Marieke Snijder, m.b.snijder@amc.uva.nl). The proposals are discussed in the HELIUS Executive Board regarding their study aims, overlap with ongoing studies, logistic consequences and financial contributions. After approval of the proposal by the HELIUS Executive Board, the collaborative research project is embedded in one of the three research areas supervised by the specific HELIUS Theme Leader.