KATHMANDU, Jan 30: Sweden's Greta Thunberg became an environmental activist after being diagnosed with the 'Asperger's Syndrome'. Asperger's Syndrome is a developmental disorder which is part of the autism spectrum and results in hyperactivity. That is, the intellectual level of a person with this syndrome is above average but such a person has difficulty socializing and communicating with other people. But Greta says that her illness is her greatest strength and that is why she has become an active environmental campaigner.