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Advice on how to cultivate happiness is hard to avoid. Magazines, online news outlets, and television news tout the best ways to improve your mood and boost contentment. Often making the list: exercise, smiling (even when you don’t feel happy), and meditation.

A systematic review published this summer in the journal Nature Human Behaviour takes a careful look at the evidence behind these how-to-be-happy strategies. Contrary to what you see in the media, the review found only weak data supporting the most commonly recommended happiness strategies. (It’s important to note that the review doesn’t prove that these strategies don’t work, just that there is not robust scientific evidence demonstrating their effectiveness.)

The review was conducted by two researchers at the University of British Columbia. They started with a Google search analysis to narrow down the most common strategies recommended in the media. The top five recommended strategies they found were (1) showing gratitude, (2) socializing, (3) mindfulness and meditation, (4) physical activity and exercise, and (5) spending time around nature. Next, the researchers looked for scientific papers investigating these strategies; in total, they found 57 quality scientific studies.

Combining the evidence, the review found “reasonably solid evidence” that expressing gratitude boosts mood, at least temporarily. They also found solid evidence that interacting with strangers and acquaintances improves mood and that acting more extraverted can enhance happiness. The researchers found some evidence that spending time with close friends and relatives boosts happiness, but the body of research on this topic was much smaller.

For meditation and mindfulness, the authors found limited studies available investigating a connection with happiness. Six large studies found that meditation improves subjective well-being, but many of these studies didn’t account for the social interaction that often accompanies group meditation practices. As a result, it is difficult to tease out whether participants felt happier because they were meditating or because they were joining a group activity.

Surprisingly, they found little evidence that regular exercise boosts happiness. Five large studies demonstrated that people feel happier after a single exercise session, but only in comparison with more boring activities, such as sitting in silence or watching a documentary on bookbinding. Researchers only found one large study demonstrating that exercise over the long term increases overall happiness.

The review authors found ample evidence that spending time in nature leads to happiness, but many of the studies were small and didn’t use robust statistical methods. But they identified four large studies that found significant evidence that spending time in nature boosts happiness.

The take-home message: Chances are the most-recommended happiness strategies boost mood and overall contentment for many people, but the scientific evidence that they work is weaker than portrayed in the media. Therefore, the real lesson of this review is that we need better studies to measure and guide implementation of happiness strategies.