Erectile dysfunction is a persistent inability to attain and maintain erection for at least 3months duration.

Normal erection can be attained due to both psychic or touching of the Instruments.
Hence when you sustained erections due to seeing of "things" or due to wild thoughts or due to fantasizing it is called PSYCHOGENIC erections.
Some persons especially people with brain injury may lost this ability.

When erections are sustained due to touching and smooching, this is called REFLEXOGENIC erections.

Some people who had stroke, head trauma may lost this type of erections.
While erections sustained during sleep and after waking up is called NOCTURNAL PENILE tumescene, its actual mechanism is unknown.

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SOURCE: https://afrib.org.ng/?p=859