A significant number of people, particularly those in their late teens, twenties, and thirties present with anxiety and depression that is linked to the abuse of 'recreational' drugs at some time in their recent past.

It is a human trait to seek out reasons for everything that happens to us, and when adult worry takes over from the, often, rash, 'nothing can hurt me' attitude of mid-adolescence and early adult, it is easy to see how somebody then suffering from anxiety and depression might buy in to the idea that the illicit drugs caused some permanent harm.
Looking at the effects of ecstasy, cocaine, amphetamines and cannabis it is entirely plausible that this worry can be well founded. 

For example, research suggests that cocaine induces panic attacks in many people and that withdrawal from it includes severe anxiety in the effects. Ecstasy too seems to induce anxiety, depersonalising and panic when taken in small or large doses and frequency and the sought after experience, while on the drug, of feeling at one with the world need not happen if the person involved already has emotional problems. Here the drug might simply exacerbate a prevailing mood. Ecstasy is also notoriously difficult to 'quality control', often being mixed with other drugs. In this case, a person with hovering obsessional problems might find themselves in deep trouble if, for example, LSD had been added.

It has been reported that ecstasy obstructs with obsessional problems and in dealing with addictions, and current research appears to suggest that even a single dose of MDMA (ecstasy) can damage the brain neurons that produce serotonin: the imbalance of which is seen by many workers in this field as a moderate to severe problem of OCD. It is not clear if this damage reverses itself once use of the drug has ceased. 

It is likely that, as with many tailored chemicals, Ecstasy & Ketamine (K or Special-K) varies widely in its effects. However, anything that may cause long-term brain damage, whatever the odds against, is probably not a good option. With regard to obsession, fear, some research also suggests that amphetamine and cocaine usage have strong links with the problem of repetitive thoughts. Amphetamine withdrawal can also induce severe anxiety and depression and again, excessive use (weekly for several months) will involve brain neuron damage that could possibly be permanent. The downside is the K hole or E hole. If you took E and K together (party/rave drug) over a few hours, you would crash into this state where it was almost impossible to snap out of whatever scenario was running in your head and bodily movement was next to impossible. Like waking up and being in a dream state where the outside world is influencing what you think but your experience is something totally surreal and then negatively effecting your sleep and dreams. Taking Amphetamines, Ecstasy, Ketamine, and LSD can also cause hallucinations and paranoia and insomnia.

As with anyone who develops a panic related disorder,
(with the help of medication and psychotherapy)
it can take years for the fear of panic to ease.

Cannabis and Marijuana seem to be interchangeable words and refer to the flowers buds and leaves of the cannabis plant. Cannabis/marijuana is often viewed as a totally harmless drug but research, again, suggests that heavy use (weekly and for several months) may make latent or existing mental disorder worse. It has also been suggested that cannabis adversely affects the hippocampus in the brain, which may limit the person's ability to learn and remember. This would not be useful in any area of life and certainly not when undertaking a programme of exposure or other activity related to overcoming an anxiety disorder that involved reinforcing learnt behaviour.

There seems to be grounds for saying that cannabis/marijuana can cause spontaneous panic in some people.  Anxious or unhappy people might be drawn to the drug as a substitute for medication, their subsequent mental problems would 'weigh' any general statistics adversely. The Australian 'Anxiety and Panic Hub' state: 'For people who are predisposed to spontaneous panic attacks, the marijuana can trigger the predisposition and contributes to sleep disorder.' 

It also seems likely that use of this drug can induce a feeling of 'loss of control' if taken in small or large doses; or if a user smokes (or eats) too much at one time. Many people with anxiety problems, and others who may not be aware that they have a potential for anxiety disorder, experience huge alarm or fear when they perceive themselves as being out of control and would never, for example, use LSD or PCP or any hallucogenic that they would be aware of as having a 'mind altering' effect. Most would not link such an effect with cannabis/marijuana/ketamine. Many people with OCD or obsessional symptoms have this problem with control and, in fact, some people cannot reach orgasm with a sexual partner for fear of losing control or of not having any control and/or lose total control and look for any fellow raver/partier for you to rub yourself up against.
 
Counseling is an essential part of drug abuse treatment for many people. Cognitive behavioral therapy, family counseling, and other therapy approaches can help people recovering from opioid addiction stay clean. Psychotherapy can also treat the other mental health conditions that often contribute to prescription drug abuse.

While any counseling therapy for drug abuse treatment is better than none. In group therapy, a person is more likely to be both challenged and supported by peers who are also going through drug rehab. Twelve-step programs like Narcotics Anonymous are the most well-known group therapy organizations.  Individual therapy can be helpful in the case of a dual diagnosis: coexisting depression, bipolar disorder, or other significant mental health condition that requires treatment in its own right, separate from the opioid addiction.

Cognitive behavioral therapy -- or CBT -- teaches a person how to recognize moods, thoughts, and situations that cause drug craving. A therapist (usually combined with a proper anti-depressant) helps the person avoid these triggers, and replace negative thoughts and feelings with ones that are healthier. The skills learned in cognitive behavioral therapy can last a lifetime, making it a potentially powerful method of drug abuse treatment. However, one needs to find psychiatrists/therapists who are trained in the complex cognitive behavioral therapy techniques.

Helpful Tips :

 Think about what you want (that's a goal), not about what you don't want (that's worry).      Goal  driven activity requires positive thinking.

Smile at strangers ...  Although this may seem a little weird, it actually makes you feel more positive and happy. You may even brighten the other person's day.

Don't give up. Good habits can replace bad ones by continuous perseverance.

Every morning, look in the mirror and think about five good qualities you have.

Notice when you are being negative, and change your thoughts to something more positive. You need to correct yourself to get better.

Volunteer. Helping others leads to a happier outlook on life.

Getting your blood flowing by exercising increases your energy. When we have energy, we think positively.

Encourage others. It's hard to be pessimistic when you are trying to lift someone else's spirits up.

Find some positive things to say and repeat them often. Use statements such as "I am a very positive person," "I am very capable," "I can do anything when I put my mind to work on it," and "I can do it."

When you feel like you're about to break, take a deep breath, count to 10, have a drink of water and smile. Even if the smile is forced, it is still a smile, and it will make you feel better. Focus on the good things.