If he is always worried that something bad is about to happen. A therapist might best diagnose Leo with: generalized anxiety disorder.
Generalized anxiety disorder can be defined as a type of disorder in which a person begins to have fear of the unknown or begins to have a negative thought which can tend to create fears in them.
A person with this type of disorder will tend to always have anxiety about things because he or she felt that something bad might likely happen.
Inconclusion a therapist might best diagnose Leo with: generalized anxiety disorder.
Learn more about generalized anxiety disorder here:https://brainly.com/question/7434259