Loneliness is a state of mind.  it means with out companions. One  important factor in loneliness is a person’s social lifes & contacts.  We depend on various people for different reasons. For instance, our family give us emotional supports, our parents and teachers give us guidance ,our friends share similar interest .

It needs to be emphasized here that but loneliness is not about how many friends /social contacts you have, it is about how many friends /social contacts we think or expect we should have.For instance lonely people may have many social contacts, they some times feel they should have more. They question their own popularity .Loneliness is a subjective experience. If you think you are lonely, then you are lonely. Even though if you are in a middle of party, u can feel lonely. Conversely a person can be alone, and not feel lonely if he has no desire for social interaction. Loneliness is an emotion, a lack, a feeling that something is missing, a pain, a depression, a need , an incompleteness, an absence.

Saturn, Venus, Ketu, 3rd,8th & 12th houses and lords are responsible for loneliness.
Planet  Saturn is father of loneliness, main reason is loneliness is our social connection with friends, family, if your Saturn is melefic then loneliness come.
Planet Venus means is god of love. Loneliness can occur in situations when some one unsucces in love so Planet Venus is important for this.
Planet Ketu is spiritual releted so it can give you loneliness if he is not in good position in horoscope.
When lords of 3rd ,8th and 12th houses are afflicting the houses of 1st ,4th and 9th or their lords, they are likely to cause loneliness.
Planet Saturn and Planet Ketu is responsible for natural  loneliness.
Lord of 3rd, 8th or 12th houses is also responsible for loneliness so try propitiating them.
If you are wearing blue sapphire, cats eye or other gemstones related to Planet Saturn & Planet Ketu or lords of 3rd, 8th and 12th houses remove them ,unless you are really sure they are good for you. Devotion towards God through sincere prayers, spells and meditation is important and safe remedies for loneliness.