There is an exhaustive list, but any impairment that affects an individual for at least 12 months, requires therapy, medication or assisting devices, while still not being fully capable of regular daily activities, would qualify one for the Disability Tax Credit.

Some of the many disabilities that may qualify:

Addictions (illegal or prescription meds)
ADHD combined type (ADHD-C)
ADHD Primarily Hyperactive/Impulsive (ADHD, ADHD-PH/I)
ADHD Primarily Inattentive (ADD, ADHD-PI)
Agoraphobia (anxiety disorder)
Alcoholic (Alcohol abuse)
Alzheimer’s disease
Amyotrophic lateral sclerosis (Lou Gehrig’s disease)
Angina
Anorexia nervosa
Anxiety
Arthritis
Asperger’s syndrome
Ataxia (Cerebellar Dysfunction)
Auditory Processing Disorder (APD)
Autism
Behçet’s disease
Bi-polar disorder (mood disorder)
Borderline personality disorder (BPD)
Bulimia nervosa
Cerebral Palsy (CP)
Chromosome Abnormality
Chronic fatigue syndrome (CFS)
Chronic pain Disorder
Colitis
Conduct Disorder (CD)
Coronary artery disease (CAD)
Cri-du-Chat syndrome (Deletion 5p Syndrome)
Crohn’s disease (Regional Enteritis)
De Vivo Disease (GLUT1 deficiency syndrome)
Dementia
Depression (Clinical, Major, Unipolar)
Developmentally Delayed (DD)
Dissociative Identity Disorder
Down Syndrome
Dressing (can’t dress or takes significantly longer)
Dysgraphia
Elimination (bowel or bladder functions)
Epilepsy
Feeding (can’t feed themselves or takes significantly longer)
Fetal alcohol syndrome (FAS)
Fibromyalgia (FM)
Gambling Addiction
Gender identity disorder
Generalized anxiety disorder (GAD)
Glaucoma
Global Developmental Delay (GDD)
Hearing Disorder (unable to hear or takes significantly longer)
Hepatitis C
Huntington’s disease
Hypermobility syndrome
Hypothyroidism
Hypotonia
Infantile Spasims (Infant Epilepsy)
Irritable Bowel syndrome (IBS)
Learning Disabilities (Special needs)
Mania
Mental illness
Mental Retardation
Microcephaly
Migraines
Mild Intellectual disability (MID)
Multiple Sclerosis (MS)
Myotonic Myopathy
Obsessive-compulsive disorder (OCD)
Oppositional defiant disorder (ODD)
Osteoarthritis
Panic Disorder
Parkinson’s disease
Personality disorder
Pervasive developmental disorder (PDD)
Post traumatic stress disorder (PTSD)
Prader-Willi syndrome (PWS)
Psychotic
Quadrapallegic
Retinoschisis
Schizophrenia
Scoliosis
Seizure Disorder
Sleep Apnea
Sleep disorder
Speech disorder (unable to speak or takes significantly longer)
Specific developmental disorder (SDD)
Stroke
Substance Abuse
Tic disorder
Tourette syndrome
Tumor
Vision (Blind in BOTH eyes, 20/200, 20 degrees field of vision)
Walking (can’t walk 100 metres or takes significantly longer)