Lisu subsistence was based on paddy fields, mountain rice, fruit and vegetables. However, they have typically lived in ecologically fragile regions that do not easily support subsistence. They also faced constant upheaval from both physical and social disasters (earthquakes and landslides; wars and governments). Therefore, they have typically been dependent on trade for survival. This included work as porters and caravan guards. With the introduction of the opium poppy as a cash crop in the early 19th century, many Lisu populations were able to achieve economic stability. This lasted for over 100 years, but opium production has all but disappeared in Thailand and China due to interdiction of production. Very few Lisu ever used opium, or its more common derivative heroin, except for medicinal use by the elders to alleviate the pain of arthritis.