It may not be a surprise to some, but millennials are engaging in very risky behavior-with their money. A new study confirmed that millennials have an alarmingly low level of financial literacy, which could have “disastrous” effects on the economy.

Among the other findings, some 30% of millennials have overdrawn their checking accounts, and 42% used “alternative financial services” such as pawnshops, auto title loans, and payday loans. Four out of five millennials have major debts such as student loans.

Millennials’ heavy debt burdens are causing them to compromise their future security. Some 17% of those with a retirement account took loans against it in the past year, while 14% took out a “hardship” withdrawal.