Several dozen African clinics and hospitals are the latest front in the battle to decipher the genetic roots of the little-understood diseases schizophrenia and bipolar disorder.

Scientists currently search for hints in genetic databases largely extracted from European and North American populations. That means they may be missing genetic variants in other populations that could help explain how the diseases develop—and how to treat them.

To broaden that genetic library, they have launched an ambitious push to collect saliva or blood samples from tens of thousands of people in Africa, Asia and Latin America, and to sequence and analyze the patients’ DNA. In recent months researchers led by the Broad Institute at the Massachusetts Institute of Technology and Harvard University have begun the project in Africa, collecting DNA samples from hundreds of patients diagnosed with psychiatric diseases.

The project faces big challenges, including a dizzying array of regulations, a lack of lab infrastructure in some places and local populations who can be wary of anything they perceive as scientific colonialism.

“Many people we want to collaborate with have experience with researchers from Europe or the U.S. who came over, conducted studies and took the samples with them. The local collaborators never heard from them. There was no effort to invest in local infrastructure,” said Karestan Koenen, a psychiatric epidemiologist at the Harvard T.H. Chan School of Public Health and an associate member of the Broad Institute, who is leading the Africa effort. “We have to build up trust, and trust takes time.”