An invisible chronic illness is a debilitating physical ailment which:

1. Others do not readily observe;
2. Continues for a long period of time;
3. Impacts sufferers to varying degrees. It might be mildly debilitating with no or limited impact to work, relationships, or activities of daily living, while other illnesses wreak havoc on careers, hobbies, socialization, and daily life activities. For example, half of U.S. adults have a chronic medical condition, 96% of which are invisible, and about 10% of U.S. adults have a condition that impairs them in their daily life activities to the extent that it is considered an invisible disability;^1-2 this is the ideal reader for this book.
4. Debilitates on a continuous or constant basis. Further, the level of debilitation is unpredictable and variable.
5. Remains stable or progresses;   
6. Includes fatigue, pain, brain fog, breathing difficulties, infections, irritable bowels, and/or neurological dysfunction. One may not always be acutely sick, but ongoing symptoms and struggles make them feel far from healthy.    

Thousands of invisible illnesses exist.  Examples include:

• Chronic fatigue syndrome (CFS)
• Sleep apnea
• Complex regional pain syndrome (CRPS)
• Cancer
• Heart disease
• Fibromyalgia
• Lupus
• Multiple sclerosis (MS)
• Mental illness
• Post-traumatic stress disorder (PTSD)
• Traumatic brain injury (TBI)
• Arthritis
• Lyme disease
• Autoimmune disease
• Diabetes
• Epilepsy
• Asthma
• Chronic obstructive pulmonary disease (COPD)
• Crohn’s disease
• Ulcerative colitis