We know that many autistic people feel lonely, but we dont know whether their loneliness changes over time. Our research study followed autistic people and people with other non-spectrum neurodevelopmental disabilities from childhood through young adulthood and asked them about their loneliness. While many people told us they felt lonely or very lonely, a sizable group also told us that they do not feel lonely. We found that people who reported feeling lonely earlier in life were likely to also report feeling lonely later in life. Overall, autistic people and people with other neurodevelopmental disabilities in our study became lonelier from adolescence to adulthood. People described multiple ways they cope with feeling lonely, such as distracting themselves or reaching out to connect with another person. People who used distraction tended to be lonelier than those who did not. Our findings tell us that there is a need for greater support of social connections for many autistic people as they become adults.