A forced psionic awakening typically occurs from a mixture of cuil exposure (both present and previous) and strong emotional neural responses, enough to form enough of the subconscious mental desire to suddenly open the person's mind to anomaly, as well as an ability relevant to this neural response. Catching someone falling, the desire to be loved, the desire to see things become real.. the desire to wipe traumatic memories, to conform with society, to even harm yourself.
A psionic disorder, or psychic disorder, is a psionic ability that is awakened that is not helpful at all, but rather harmful to one's self. A psionic disorder may have been helpful when it first awakened, such as by saving the user in some mental or physical trouble, but the side effects of such an ability prove to be more detrimental than helpful, and above all - uncontrollable. Some disorders can even become progressively worse, forcing those they afflict to find ways to cope, cure, or even make use of it.
Most often psionic disorders are self-affecting, meaning they target the user instead of anybody else. Disorders from every subject can affect the user in some way, such as neuroinvasive abilities that alter the user's memory or emotions or induce hallucinations, or metamanipulative abilities that biokinetically negatively affect the user.
Dealing with psionic disorders can be very difficult, and widely depends on the specific nature of the disorder. Many simply cope with it, but some choose to seek specific means of dealing with the disorder, whether from themselves or outside forces. If your character has a psionic disorder, dealing with it will be a major part of their character story - will they live with it? Search for a cure? Or will they bend it to the best of their abilities?
Psionic disorders must be applied for the same way abilities are, since they are just abilities that are harmful to the user. An existing psion with a disorder is someone who is already dealing with it, whereas an awakening psion with the disorder is someone who will develop the disorder from their awakening event. Psionic disorders follow the standard ability application.