Zookeepers at Poland’s Warsaw Zoo have announced a new project testing whether CBD oil can help to reduce symptoms of anxiety and depression in elephants.

Zookeepers at Poland’s Warsaw Zoo are launching a project to test whether CBD oil can help reduce anxiety in animals, the BBC reports. Fredzia, a female elephant who is grieving following the loss of the herd elder, will be the first animal to receive the treatment.

Dr. Agnieszka Czujkowska, head of the zoo’s Animal Rehabilitation Department, told the BBC that Fredzia had “reacted strangely” when she saw the dead body of Erna, the herd leader and its largest female. Fredzia displayed signs of stress and depression and struggled to establish a new relationship with her female companion. Czujkowska said elephants are prone to stress but easy to monitor, making them ideal for the study.

The first part of the trial included collecting fecal, saliva, and blood samples to monitor the animals’ cortisol levels. Cortisol is produced by humans and animals when stressed. The oil will next be administered to the elephants via their food or directly into their mouths. The zookeepers will then measure their cortisol levels again to see whether the CBD is working to reduce their stress.

The results of the study are not expected for at least two years. If successful, the zoo plans to expand the project to other stressed animals, including bears and rhinoceroses.

While there are CBD products marketed for animals, there are no comprehensive studies showing efficacy for the cannabis-derived compound related to animals and stress. In February, researchers at Texas’ Tarleton State University’s Equine Center announced a study examining whether CBD can reduce anxiety for horses with plans to publish the results next year.