Being a mentally healthy person does not necessarily mean the same thing to everybody. Normal and abnormal are relative. The American Psychiatric Association published the Diagnostic and Statistical Manual of Mental Disorders (DSM) to put clear guidelines for mental disease diagnosis and treatment strategies. This manual is used by insurance companies to determine health coverage.
The World Health Organization (WHO) also produced a mental disorders guide as a part of its International Classification of Disease. A different guide than the DSM and the WHO classifications is used in China.