If you resolved to be happier this year, you may be considering some kind of therapy to help you figure out the beliefs or self-defeating ways of thinking that may be leading you to feel down on yourself and depressed. And for reasons of money or convenience, you may be tempted by one of the many online programs and apps designed to help you do this, but wondering which to choose — or if an app can work at all.

A study that took a broad look at the issue of internet-based therapy offers some hopeful news for people seeking to work online on the mental habits that can lead to depression. Researchers from Indiana University analyzed the results of 21 studies that had focused specifically on internet-based cognitive behavior therapy (iCBT).

Conventional methods — talking to a trained therapist in person — may still be more effective; but for those who don’t have access to talk therapy because of distance, time constraints or cost, the study provides some great news.

The regular (non-internet) version of CBT is a form of talk therapy, in which the therapist typically helps a person identify patterns of behavior or reactions that are counterproductive and contribute to depression, and then helps them replace these reactions with more productive, healthier ones. Online versions of the therapy also ask users questions designed to illuminate the personal behaviors and emotional responses that may be affecting them.

A total of about 4,800 participants were included in the meta-analysis. Most studies compared participants given real iCBT apps with those given a “fake” app offering less effective recommendations, or placing them on a wait-list to receive therapy. People in the studies had depressive symptoms that ranged from mild or moderate depression to severe depression, so the researchers could see if iCBT would work for varying degrees of depression.

“Before this study, I thought past studies were probably focused on people with very mild depression, those who did not have other mental health problems, and were at low risk for suicide,” said study author, Lorenzo Lorenzo-Luaces, in a statement. “To my surprise, that was not the case.”

He and his team found that the apps were very effective overall — and for people with all types of depression, even severe depression.

This is great news, since depression is now the leading cause of disability worldwide, and millions of people in the U.S. are living with it. In fact, Lorenzo-Luaces says that the number of people needing treatment is greater than the number of therapists who can provide therapy to them.

“Close to one in four people meet the criteria for major depressive disorder. If you include people with minor depression or who have been depressed for a week or a month with a few symptoms, the number grows, exceeding the number of psychologists who can serve them. iCBT apps take the methods we have learned and make them available to the many people who could benefit from them. It's an exciting development.”

People shouldn’t ditch conventional methods — talking to a trained therapist in person — if they’re working for them. “This is not to say that you should stop taking your medication and go to the nearest app store,” Lorenzo-Luaces added. “People tend to do better when they have a little bit of guidance.”

Future studies will have to look into whether and how app-based therapy compares to in-person therapy. But for those who don’t have access to talk therapy because of distance, time constraints or cost, the study provides some great news. Relief from depression symptoms based on the tried-and-true methods that psychologists have been using for years may literally be in your pocket.

The study is published in the Journal of Medical Internet Research.