Source: Flickr via user Mark.

Legalized marijuana has taken the investing world by storm. According to Arcview Market Research, the industry generated $1.53 billion in revenues in 2013, and early estimates have this number jumping to $2.5 billion in 2014-- a remarkable 40% growth rate year over year.

With 23 states now having decriminalized marijuana for medical purposes, the industry is poised to become one of the fastest-growing industries of all time. Investors have thus plowed into so-called marijuana stocks with gusto, causing share prices to skyrocket.

Last year, for instance, the medical marijuana distribution company Medbox (OTC:MDBX) saw its share price rip higher by a jaw-dropping 612% in only a few short days. 

And GW Pharmaceuticals (NASDAQ:GWPH), the medical cannabis company and maker of Sativex, indicated for multiple sclerosis spasticity, has also benefited greatly from the general marijuana craze, with its shares gaining nearly 1,000% within a mere 10-month span at one point.

Since then, the reality and hardships of commercializing a product that is still illegal at the federal level have kicked in, causing these two bellwether marijuana stocks to pull back in a huge way from their former highs.

Even so, legal marijuana advocates believe these and similar companies will eventually become stable long-term investments.

Legal cannabis has a long way to go to even touch this single drug
While investor enthusiasm for marijuana stocks might be warranted over the long haul, I think it's important to understand the current place of these stocks within the broader health care sector.

Source: AbbVie.

To do so, let's consider how the entire industry fares against a single drug -- namely, AbbVie's (NYSE:ABBV) Humira. In 2013, this anti-inflammatory drug became the world's best-selling drug by posting over $11 billion in sales and growth rates that have regularly exceeded a staggering 15%.

Even with the launch of Gilead Sciences' (NASDAQ:GILD) behemoth hepatitis C drug Sovaldi, Humira should still top the list of best-selling drugs in 2014. According to AbbVie's third-quarter earnings release, Humira was on track to generate $13 billion in total sales last year, with the final numbers to be released in the upcoming fourth-quarter earnings.

This single pharmaceutical is thus estimated to have sold more than five times the entire legalized marijuana industry last year.

With AbbVie in hot pursuit of additional indications for Humira, including gaining one more recently in pediatric Crohn's disease, Humira's incredible growth story is far from finished. In fact, legalized marijuana probably won't stand a chance of generating more revenue than Humira until 2018, at which point the combination of the potential loss of patent protection for Humira and the marijuana industry's organic growth could turn the tables. 

Here's the broader point
Investors looking to catch the next "big thing" in marijuana stocks should consider a few critical issues before diving into these highly speculative companies. First off, marijuana companies have proven to be extremely volatile investing vehicles because of the uncertain nature of the industry's legal basis going forward.

Federal agencies, such as the DEA, are still raiding marijuana dispensaries in states that have decriminalized such businesses, and the incoming Congress looks decidedly more conservative than its predecessors in terms of potentially legalizing marijuana at the federal level. Put simply, the hazy legality of marijuana may act like a governor on the industry's growth rate, especially in this shifting political climate.

Investors seeking outsized gains certainly haven't necessarily had to rely on risky marijuana stocks. AbbVie's shares, for example, have steadily marched northward since the company split from Abbott Laboratories in 2013:

ABBV Chart

AbbVie has also raised its dividend twice within the past year and will probably do so again in 2015, as it ramps up its hepatitis C therapy Viekira Pak.

If you bought in right after the split and reinvested the dividends, this seemingly boring health care stock would have more than doubled your money -- all the while having nowhere near the level of volatility seen in marijuana stocks.

They may not make you rich overnight, but dividend-paying companies such as AbbVie are proven long-term winners. Marijuana stocks, on the other hand, are likely to see more volatility as the legal process unfolds and simply don't offer a straightforward path toward wealth creation.