118 is a good score. Go take some non-verbal reasoning tests if you want to affirm what your test administrator suggested about your ability to solve problems. There are a select few good ones on-line that are standardized.
Take up a significant reading and writing habit. However, the key is that the reading has to get progressively harder (undergrad level>grad level>etc..) over time. If there is material out there that is over your head, no matter what it is (science, philosophy, etc.) work up to mastering it (reading) to the point where you can build new models using the rules that the material presents, when applicable. Being able to construct valid and novel models (problem solving), on the fly, is a sign of the intelligence that your psychiatrist thinks is latent in you. If you can, get a graduate degree in the sciences if you don't have one. Yes, that means starting with an undergrad degree in the sciences, usually. This will train your mind and help to refine, first, a work ethic for learning, and second, every undeveloped ounce of intelligence. If you aren't an experienced writer, your writing sucks. Trust me. Writing alone won't improve your IQ, but it is a good practice that assists you in organizing and presenting complex logic, and therefore helps your thought processes and therefore your overall process towards developing intelligence. Be sure to keep your writing, as you will be able to look back after only a few years of this process and affirm what a retard you before were

. I would suggest that taking non-verbal reasoning tests helps, but in reality I think that repetitive testing just incurs a retest effect. They are only for occasional measurement.
These activities will have an effect on your ability to solve problems, over time. The key is to never assume that you have reached your potential for knowledge, or a zenith of conclusive reason in any subject matter. Always assume that
the only thing that you know is that you don't know. This will keep you from hitting intellectual dead-ends that are constructed only by your ego. You can work and live your life by the most probable models of the world that you have come across, but never take anything as an absolute truth. Always be ready to learn.
I only took an intelligence test later in life, but using my SAT percentile rank and my score as a proxy for intelligence (charts can be found online), I score significantly higher these days on both intelligence tests and standardized scholastic tests. I can read, process, and infer much more information now than I before could, due to a decade of reading material that challenged me.
No amount of pill popping will have a dramatically positive effect on intelligence or it's mimic, a trained learned mind, that pursuing one of the above suggestions will. It's impossible. If intelligence isn't genetically determined (I believe that it is to a large extent), then the above process will have no limit on its helpful effect. If intelligence is genetic, then the above process will aid in bringing that intelligence to the surface and refining it. Unless your mind is trained for logic, then all of the intelligence in the world won't help, and likely it will lead you down some unsavory paths as your intelligence looks for outlets in unproductive places. In a way, rote learning can often mimic verbal intelligence (not problem solving) better than intelligence can, assuming the wrong people haven't gotten a hold of you. Problem solving abilities can be refined to a great degree through practice, but I doubt that you can significantly improve your actual innate capacity for solving problems, beyond what is merely an undeveloped talent.
Edited by golgi1, 29 October 2012 - 04:23 AM.