What are the four phases of clinical research trials?

Children with neurological and developmental disorders often experience chronic sleep disturbances. Melatonin has been commonly prescribed because of its hypnotic properties. However, trials have had conflicting results. Therefore, researchers assessed the effectiveness of melatonin in treating severe sleep problems in children with neurodevelopmental disorders. A randomised double blind placebo controlled multicentre trial study design was used. The intervention was immediate release melatonin capsules given 45 minutes before the child’s bedtime for a period of 12 weeks. Treatment started with a 0.5 mg capsule, and escalated through 2 mg, 6 mg, and 12 mg, depending on the child’s response to treatment. Participants were 146 children who had a severe sleep problem and had not responded to standardised sleep behaviour advice provided to parents four to six weeks before randomisation. Children were recruited from 19 hospitals across England and Wales. The children were randomised to melatonin (n=70) or placebo (n=76). The outcome measures included subjective (as assessed from sleep diaries completed by the parents) and objective (as recorded by actigraphy) measures of sleep. The researchers reported that children gained little additional sleep on melatonin compared with placebo. However, the children receiving melatonin fell asleep significantly more quickly and they awoke earlier. Which one of the following best describes the phase of the above clinical trial? a) Phase I