What is the benefit of solitude?
solitude is a state of seclusion or isolation
Are there any health effects to solitude?
short term  solitude is often valued as a time when one may work
When did the practice of solitude start?
last 6 months
I mean how far back can we trace the history of when people started the practice of solitude?
, these two words refer, respectively, to the joy and the pain of being alone.
Health effects.
Symptoms from complete isolation, called sensory deprivation, often include anxiety, sensory illusions, or even distortions of time and perception. However, this is the case when there is no stimulation of the sensory systems at all, and not only lack of contact with people. Thus, by having other things to keep one's mind busy, this is avoided.
Still, long-term solitude is often
Solitude
Solitude is a state of seclusion or isolation, i.e., lack of contact with people. It may stem from bad relationships, loss of loved ones, deliberate choice, infectious disease, mental disorders, neurological disorders or circumstances of employment or situation (see castaway).
Short-term solitude is often valued as a time when one may work, think or rest without being disturbed. It may be desired for the sake of privacy.
A distinction has been made between solitude and loneliness. In this sense