Per
ADAA.org, approximately 50% of adults with AD/HD(which includes "ADD") also have an anxiety disorder.
Per
aspergerfoundation.org.uk, a person with Asperger's Syndrome is especially susceptible to high levels of anxiety.
According to Clinical Psychiatry News,
Hoarding behavior associated with traumatic life events More than 54% experienced more than one TLE (Traumatic Life Event), and the maximum number reported was five. A motor vehicle accident was the most commonly reported trauma. In addition, hoarders were more likely than nonhoarders to report rape, sexual abuse, and having witnessed a crime, according to a subanalysis of specific TLEs. Pure hoarders reported a significantly greater number of TLEs (odds ratio 2.27), Ms. Cromer said.
(Note: My understanding is that hoarding has been classified in the DSM IV-TR as falling under OCD, but my understanding is the DSM V will re-classify hoarding as a separate diagnosis. Some people who hoard have symptoms of OCD and some do not. Hoarding also happens amongst those with schizophrenia and dementia, and it also happens independent of other diagnoses.)