Millennials are too conservative in their investment choices, according to a new report from the Wells Fargo Investment Institute. They’re holding too much cash and bonds and too little stocks in their investment accounts.

(Related: How Prepared Are Boomers, Gen Xers & Millennials for Retirement?)

The analysis of 904,000 Wells Fargo Advisors accounts studied the investment allocations among different generations: the silent generation, born between 1928 and 1945; baby boomers (1946-1964); Gen Xers (1965-1981); and millennials (1982-2000).

Every generation held too much cash, and every generation except millennials held too few bonds compared to the average asset allocations of U.S. target date funds reported by Morningstar.

“In general, we have found that generations do not invest all that differently, but perhaps they should,” the report notes.

The oldest cohort, however, had too large an equity allocation, which was only slightly true for baby boomers, but Gen Xers, like millennials, held too few stocks.

Sameer Samana, global quant strategist for Wells Fargo Investment Institute, said Gen Xers may be too timid about equities because they graduated college just when the tech bubble was bursting. That was followed years later by the financial crisis and Great Recession, which unnerved both Gen Xers and millennials.

“Millennials saw the world in crisis mode” and many are “hampered by monthly payments for student debt,” says Samana, explaining millennials’ tilt toward more cash and conservative investments.

(Related: How American Families Pay for College: 2017)

About 34% of millennials carry student debt, with the median balance of most under $20,000, and 75% of those holding debt say it is “unmanageable,” according to the Wells Fargo Millennial Survey published a year ago.

Looking ahead, Wells Fargo Institute expects millennials and Gen Xers will likely adapt the same financial habits of the generations that preceded them as their needs change, as they form families, buy homes and then focus more on retirement.

— Check out Married Women Need Their Own Financial Plan: Study on ThinkAdvisor.