Six middle- and high-school students watched a psychologist write three letters on a whiteboard: O-C-D.

“What does OCD stand for?” asked psychologist Avital Falk.

“Obsessive-compulsive disorder,” answered a timid 12-year-old wearing a red tie.

“What makes it a disorder?” Falk asked.

“Because it’s messing up our lives,” said Sydney, a chatty 14-year-old.

These young people have OCD, an illness characterized by recurrent, intrusive thoughts and repetitive behaviors, or other problems with anxiety. They also are participants in a novel treatment program at Weill Cornell Medicine in New York.

Typically patients with OCD see a therapist once a week for an hour over several months, but this program consists of two-hour group meetings three times a week, plus up to four additional hours of individual therapy per week. Some patients complete the treatment in just two weeks.

The program, which began in 2016, is part of a new wave of concentrated, intensive therapy programs for psychiatric disorders. The Child Mind Institute in New York launched a two-day “boot camp” for teens with social anxiety last year. The Houston OCD Program in Texas operated its first weeklong treatment program for adolescents during spring break.

In Atlanta, Emory University is in its third year of a two-week therapy program for veterans with post-traumatic stress disorder, funded by the Wounded Warrior Project.

The approach is gaining popularity in part because of new research showing that for both adults and children, the concentrated approach is generally just as effective, and in some ways more effective, as treatment that is spread out over several months. A meta-analysis of randomized, controlled trials found remission rates of 54 percent for children in intensive, concentrated cognitive behavioral therapy (CBT) for anxiety disorders and 57 percent for those in standard CBT, a difference that was not statistically significant.

The intensive treatments seem to work best for anxiety-related disorders.

Supporters of the approach said that while it may involve a similar number of total hours as weekly therapy, relief is quicker. Thomas H. Ollendick, a psychology professor at Virginia Tech, who helped pioneer a one-day treatment for phobias, said this can be crucial for people whose illnesses are preventing them from attending school or work.

But it also has downsides. The price tag for the Houston spring break program, for example, was $2,500 for the week. Many programs do not accept insurance. Sometimes insurance companies will reimburse for only a small portion of treatment or will require patients to first prove that less intensive therapy has failed before coverage kicks in.

Patients also need to be motivated and ready and willing to move quickly into exposure work, said Donna B. Pincus, director of the Child and Adolescent Fear and Anxiety Treatment Program at Boston University.