False.
A theory hasn't been scientifically confirmed, since it's just an idea, a concept. Though they have not been officially proven, they are still really reliable because even before becoming a theory, a hypothesis needs to undergo tests (experiments).
When a theory is proven, it becomes are fully reliable source supported by tests observations and evidence.
Hope it helped,
BioTeacher101
(If you have any questions, feel free to ask them in the comments)