The statuory definition of disability specifies that you must have a “medically determinable physical or mental impairment”.
A medically determinable physical or mental impairment is an impairment that results from anatomical, physiological, or psychological abnormalities which can be shown by medically acceptable clinical and laboratory diagnostic techniques. A physical or mental impairment must be established by medical evidence consisting of signs, symptoms, and/or laboratory findings-not only by the individual’s statement of symptoms.
By definition, those impairments which cannot be proven by an objective medical test (such as an X-Ray or MRI) are more difficult to prove. For example, the diagnosis of fibromyalgia relies significantly on the patient’s subjective complaints. There is not an X-Ray which will prove the existence of fibromyalgia. That is why these types of soft tissue disorders are more difficult to prove than say a “broken back”, which can be proven with an MRI. Moreover, the above definition means that mental disorders are difficult to prove. Not impossible to prove. Just more difficult because you cannot exactly prove a disorder like bipolar disorder with an X-Ray.
In short, some disorders are more difficult to prove than others. This is why the claimant’s credibility and medical records are so important.