WASHINGTON (AP) — U.S. consumers expanded their borrowing at a slower rate in June compared to the prior month.

Overall credit rose by $18.3 billion in June to a total of $3.17 trillion, the Federal Reserve said Thursday. The rise was down from a gain of $21.5 billion in May.

The smaller increase suggests that consumers remain sheepish about spending, which could limit how fast the economy can grow. Rising debt loads are generally a sign of greater confidence in the economy and fuel faster growth.

Auto and student loans drove much of the gains in June, up $16.2 billion. They have risen 8.4 percent year-over-year.

Credit card debt increased by a slight $2.1 billion in June. The increase in credit card debt over the past year has been 1.3 percent, evidence that consumers are restrained.

Americans still have a limited appetite for debt after gorging themselves on sub-prime mortgages and credit cards before recession seized the country in late 2007.

When the rate of borrowing increases, growth usually accelerates. People increase their spending on the assumption that they will have income to repay the debt, kicking off a cycle that leads the economy to grow faster and potentially overheat.

The most recent credit cycle was broken by the housing bust and the Great Recession. Millions of people lacked the income to pay their mortgages, in some cases because they lost their jobs following the downturn that began in late 2007.

Over the five years in which the country's economy has rebounded, Americans have remained hesitant to take on debt. Consumer spending growth has averaged a tepid 2.2 percent a year during the recovery, compared to a 2.9 percent average during the previous expansion.

The average household debt-to-income ratio has fallen to 77 percent from the 2008 peak of 95 percent, according to analysis by the bank HSBC. That debt ratio remains higher than the 69 percent average in 2001.