​More than eight in 10 Americans support legalizing marijuana for medical use, according to a new poll. Almost half favor decriminalizing the herb completely.

According to the new ABC News/Washington Post national poll, 81 percent support legalizing cannabis for medicinal use, up from already sizable 69 percent support in 1997.

Support for both medical marijuana and decriminalizing for all adults is far higher than it was a decade ago, reports poll analyst Gary Langer at ABC News

Fifty-six percent say that if medical marijuana is allowed, then doctors should be able to prescribe the herb to anyone they think it can help.

​Separate from medical marijuana, many recent efforts have focused on decriminalizing marijuana for all adults. Both legislation and, separately, ballot initiatives, are circulating in both Washington state and in California in 2010.

Recent polls in both Washington and California have shown support for legalizing pot to be at 56 percent, so if one of these ballot measures comes to fruition in November, either state could become the first in the nation to remove all criminal penalties for marijuana.

Age is a big factor in support for changing marijuana laws. A majority of adults under 65 — 51 percent — support legalization, while just 23 percent of senior citizens think we should loosen up on pot.

Political and ideological affiliations matter, as well. Liberals favor legalization at 63 percent, while only 30 percent of conservatives want to legalize pot. Fifty-three percent of Democrats want to legalize, while on 32 percent of Republicans agree.

But medical marijuana receives majority support across the political and ideological spectrum.

Even conservatives, at 68 percent, and Republicans, at 72 percent, support legalizing medical marijuana. Support is even greater among liberals (90 percent) and Democrats (85 percent).

Support for medical marijuana slips to 69 percent among senior citizens, with 85 percent of all adults under 65 supporting medicinal pot.,

While, as noted above, 56 percent prefer no restrictions on to whom medical marijuana should be available with a doctor’s prescription, 21 percent say it should be limited to terminally iull patients. An additional 21 percent believe pot should be limited to those with serious, but not necessarily terminal, illnesses.

Liberals are 23 points more likely than conservatives, and Democrats 20 points more likely than Republicans, to oppose government restrictions on medical marijuana, preferring to let doctors make the decision. There’s also a gender difference, with men 10 points more likely to say only the doctor, not the government, should decide who gets medical pot.

The main difference is whether folks think medical marijuana should be permitted in the first place. Among supporters, 63 percent would rely on the doctor’s discretion. Among those who oppose medical pot, 75 percent say that if it is allowed, it should be limited to seriously or terminally ill patients.

The ABC News/Washington Post poll was conducted by telephone Jan. 12-15, 2010, among a random national sample of 1,083 adults, including landline and cellphone-only respondents, with an oversample of African Americans (weighted to their correct share of the population) for a total of 153 black respondents. Results for the full sample have a 3.5-point margin of error.