Specific phobias have a one-year prevalence of 8.7% in the USA with 21.9% of the cases being severe, 30.0% moderate and 48.1% mild. The usual age of onset is childhood to adolescence. Women are twice as likely to suffer from specific phobias as men.

Evolutionary psychology argues that infants or children develop specific phobias to things that could possibly harm them, so their phobias alert them to the danger.

The most common co-occurring disorder for children with a specific phobia is another anxiety disorder. Although comorbidity is frequent for children with specific phobias, it tends to be lower than for other anxiety disorders.

Onset is typically between 7 and 9 years of age. Specific phobias can occur at any age but seem to peak between 10 and 13 years of age.

Gerascophobia is an abnormal or incessant fear of growing old or ageing.

Gerascophobia is a clinical phobia generally classified under specific phobias, fears of a single specific panic trigger. Gerascophobia may be based on anxieties of being left alone, without resources and incapable of caring for oneself. Sufferers may be young and healthy.

Symptoms include the fear of the future and the fear of needing to rely on others to do daily functions. Many also fear they will not play an active role in society when they get older.

The term "gerascophobia" comes from the Greek γηράσκω, "gerasko", "I grow old" and φόβος, "phobos", "fear". Some authors refer to it as gerontophobia, although this may also refer to the fear of the elderly.

A specific phobia is any kind of anxiety disorder that amounts to an unreasonable or irrational fear related to exposure to specific objects or situations. As a result, the affected person tends to avoid contact with the objects or situations and, in severe cases, any mention or depiction of them. The fear can, in fact, be disabling to their daily lives.

The fear or anxiety may be triggered both by the presence and the anticipation of the specific object or situation. A person who encounters that of which they are phobic will often show signs of fear or express discomfort. In some cases, it can result in a panic attack. In most adults, the person may logically know the fear is unreasonable but still find it difficult to control the anxiety. Thus, this condition may significantly impair the person's functioning and even physical health.

Specific phobia affects up to 12% of people at some point in their life.