Some are unsure whether these apps work. "It's too early to be 100 per cent certain, but the evidence is mounting," says game developer Scott Crabtree, who points to a Norwegian study titled Better Days.

The study, released by , gauged the impact of internet-based positive intervention involving about 200 people. It explored gratitude, acts of kindness and mindfulness. The result was encouraging: there was a small but significant positive effect on mood.

Another study, published in , assessed an emerging cognitive treatment for stress, called "attention-bias modification training" (ABMT) - the basis of Personal Zen. For the study, about 75 participants, who scored highly in a stress survey, tracked two moving onscreen characters.

After playing the game for either 25 or 45 minutes, the participants had to present a speech in front of a camera - a tough task given their high-strung temperaments.

Those who played the game version showed lower anxiety during their talks, and reported less negativity than placebo group members.

Even the 25-minute session had potent effects on stress measured in the laboratory, fuelling the claim that ABMT could act as a "cognitive vaccine" against anxiety.

Yet Crabtree suggests that the new breed of positive apps might be hyped. Beware of bullish studies produced by sources touting them, he says. "Whenever the source of the data is someone profiting from the data, you must take a somewhat sceptical view."

Another reason for doubt is the lack of vital face-to-face human contact. "Electronic happiness boosters are effective and cost-effective, but they will never replace warm human relationships," he says.

Nor will they replace "real-world interventions". "That is, you'll get more of a boost by exercising with a friend outdoors in good weather," Crabtree says.

But he still sees a bright future for anti-anxiety apps, which he says, have been proven effective, empowered by the brain's rewiring ability called "neuro-plasticity".

"Neuro-plasticity is an undisputed fact now, and evidence is strong that video games, and almost everything else we do rewires our brains," he says.

Ofer Leidner, the co-founder of Happify and a technology-trained economist, began exploring brain plasticity after building a career in the casual games sector.

Inspiration hit after his future company co-founder, fellow Tel Aviv university graduate and computer scientist Tomer Ben-Kiki, learned about the work of the so-called father of positive psychology Martin Seligman at a conference. Ben-Kiki gave Seligman's 2011 science-based book on the topic, , to Leidner.

After further investigation, the pair decided to marry the supposed science behind what makes us happy with their gaming development skills, and build an app that teaches the secrets on the back of suggested daily goal-based activities.

Happify was the result.

Eighty-six per cent of regular users report increased levels of happiness after a few weeks, Leidner says.

He adds that he works closely with a team of positive psychology researchers from colleges including Harvard and Stanford to ensure that the content he designs is true to science and teaches the skills he aims to instil.

Research and development engineer Marshall Barnes, who has a broad background in technology-oriented consciousness research, says any game that supplies an enjoyable stimulus can contribute towards mood enhancement.

Barnes cites a post published by the self-improvement site Daily Burn, which claims that brain apps can help you gain control over your emotional state.

Positive Activity Jackpot, an app designed to help post-traumatic stress disorder sufferers, particularly interests Barnes. There is a market for mood enhancement technology, he says.

Self-styled "geek therapist" Steve Kuniak, one of a growing number of counsellors who use video games and other tech tools at work, says games may augment everyday therapeutic practices such as socialising, exercising and a good diet.

The joy of games is that they provide a great space for being present and mindful, according to Kuniak. Achieving that mental state may counter depression caused by rumination, and anxiety caused by a dread of the future, he says, citing positive psychology research.

His advice: favour games that are attractive enough to spark engagement anchored in substance. If one claims to be backed up by research, read it before making an informed judgment, he says, adding that games are no miracle cure.

Likewise, Leidner admits he is not offering a magic pill - you cannot click your way to happiness, he says.

If you are seriously feeling down or disturbed, experts say, you should follow the orthodox path, and see a therapist.