<human>:  Can you tell me the leading causes of homelessness in the US?
<bot>: There are more than 630,000 homeless people in the US, and many of these are homeless children and youth. Approximately 60% are living in cars, RVs, or shelters; 28% are sleeping rough, and 14% are doubled up with other families or friends. About half of homeless people have a mental illness, and about a quarter have a substance use disorder. Almost a quarter of homeless people are unemployed, and 23% of homeless families are headed by women