Group therapy exponentially increases the complexity of any situation. Ask any parent whether having another child increases the work or makes it easier, majority will say it quadrupled it rather than making it easier. Adding one person, a family or several people to a session has the same effect. Nevertheless, the positives out weigh the negatives; you just need to decide which type of group therapy you are looking for.
Content focused and educational. For example: Parental classes, Addiction for families, Domestic violence, and Marital enrichment. Being educational this group could be larger than most but does depend on the audience. For example for children, families, or couples there should be no more than 10 people; for adults or adolescents there could be as many 25-30 people in attendance.
These focus on interpersonal process and though typically a group of individuals, families and couples are increasingly being drawn to these type of groups. Typical process groups could be for those dealing with grief & loss, divorce, addiction, or even trauma. For this group there should be between 4-8 people to be effective.
Is as it states, a combination of the first two groups. It may be educational for those affected by addiction but giving the opportunity to discuss and process thoughts and feelings that the discussion brought up. Recommended group size for this group can 4-12 individuals, couples and families; 2-6 individuals if it is aimed towards children.
OPEN VS. CLOSED GROUPS
With open groups individuals do not need to wait to join, they can join as soon as convenient for them whilst their motivation is high. Closed groups on the other hand allow for intimacy and trust to develop, as no new members will be joining until the next scheduled group. This form of group is typical for process and court mandated psycho-educational groups.