Outlook

Nations with cannabis programmes should respond to a lack of research. Canada can be a leader, say Jonathan Page and Mark Ware.

Pharmaceutical research into the chemicals found in cannabis has so far supplied only one licensed medicine. But scientists think there could be hundreds more.

Researchers are gathering clinical data for medical marijuana against a backdrop of deregulation and opportunism.

Neuroscientists are learning how to repair neural circuits damaged by addiction.

Research into addiction explores many aspects of how and why this disease develops. Here are four of the toughest questions.

Addiction is a devastating disease that alters the brain's circuitry, notably in young adults. But the changes need not be permanent: improved understanding of them will help in developing ways to lessen the burden. By Margaret Munro. See a Nature Video at go.nature.com/e1gqkk.

More research, and dedicated funding, is needed to understand and successfully treat compulsive habits, says Marc Potenza.

The role of temperament, metabolism and development make the inheritance of addiction a complex affair.

To treat addiction, people need help to develop psychosocial skills in addition to taking medication, says Kenneth E. Leonard.

Ingenious pill formulations and the latest manufacturing technologies are helping to stem the tide of painkiller addiction.

Addiction researchers are optimistic that they can create effective medication to treat addictions. But the key question is, will pharmaceutical companies bring them to market?

Giving a gift or a cash incentive to someone to give up an addiction sounds like a prize for behaving badly, but the practice works. The real challenge is deciding who should pay for it.

The Index's leading countries and institutions for high-quality science, ordered by weighted fractional count (WFC) for 2014. Also shown are the total number of articles, and the change in WFC from 2013. Articles are from the 68 natural science journals that comprise the Nature Index (see Guide to the Nature Index, page S30).

Bees do far more than just make honey. Globally, the 25,000 or so bee species play a crucial part in crop production and in promoting biodiversity.

Of all insects, bees — especially honeybees (Apis mellifera) — are the most lauded by humans. They have been praised by poets and writers, including Virgil and Shakespeare, and their colonies are seen as a metaphor for human societies. This affinity is no surprise: humans and bees have a long and interwoven history.

Solitary bees receive scant attention, but research shows that they are vital pollinators of crops and wild habitats.

A growing understanding of insect flight is helping scientists to build tiny flying robots.

Charles Michener has been studying bees for more than 80 years, and, although he has seen many changes in the field, his interest in these insects has not diminished. Now aged 96, he contributes to bee research as a Watkins distinguished professor emeritus at Kansas University in Lawrence.